Ultrasound diagnostic apparatus, method of producing ultrasound image, and recording medium

ABSTRACT

Ultrasonic transmission and reception for sound speed setting is performed in response to an instruction to freeze, an instruction on an observation target range, an instruction to change image quality and an instruction to change an image mode, a reception signal obtained by the ultrasonic transmission and reception for sound speed setting is used to set the sound speed in a subject, and a reception signal obtained during ultrasonic transmission and reception is processed based on the set sound speed to produce an ultrasound image. Such method makes it possible to produce a high-quality ultrasound image subjected to delay correction appropriate to various operations on an ultrasound diagnostic apparatus, such as freezing and change in image quality.

BACKGROUND OF THE INVENTION

The present invention relates to an ultrasound diagnostic apparatus.Specifically, the present invention relates to an ultrasound diagnosticapparatus which allows stable display of a high-quality ultrasound imagewhen various operations, such as freeze and change of image quality, areperformed in the ultrasound imaging apparatus, a method of producing anultrasound image, and a recording medium.

An ultrasound diagnostic apparatus using an ultrasound image hashitherto been put into practical use in the field of medicine.

In general, this type of ultrasound diagnostic apparatus is composed ofan ultrasound probe (hereinafter, referred to as a probe) which has apiezoelectric element array in which piezoelectric elements to performtransmission and reception of ultrasonic waves are arranged, and adiagnostic apparatus body.

In the ultrasound diagnostic apparatus, an ultrasonic wave istransmitted from the probe toward a subject, an ultrasonic echo from thesubject is received by the probe, and the reception signal iselectrically processed in the diagnostic apparatus body to produce anultrasound image.

In the piezoelectric element array of the ultrasound probe, anultrasonic echo by single transmission of an ultrasonic beam is receivedby a plurality of piezoelectric elements. Accordingly, even if theultrasonic echo is reflected at the same reflection point, the timeuntil the ultrasonic echo enters each piezoelectric element differsdepending on the position of the piezoelectric element.

For this reason, in the ultrasound diagnostic apparatus, delaycorrection using a delay time according to the position or the like ofeach piezoelectric element is performed on the reception signal outputfrom the ultrasound probe, phase focusing is made by the delaycorrection, and phasing addition is performed to produce a sound raysignal (sound ray data), thereby producing an appropriate ultrasoundimage with no distortion.

The delay correction is performed using a sound speed of an ultrasonicwave (hereinafter, also simply referred to as “sound speed”) in thesubject. In conventional the ultrasound diagnostic apparatus, on theassumption that the sound speed is constant, the value of the ultrasonicwave sound speed set as the whole of the apparatus is fixed to a certainvalue (for example, 1530 m/sec).

However, since the sound speed differs due to a difference of a tissue,such as a fat layer or a muscle layer in a living body, the sound speedof the ultrasonic wave in the subject is not uniform. Further, a stoutsubject and a thin subject are different from each other in thethickness of the fat layer or the muscle layer.

For this reason, in the conventional ultrasound apparatus in which thesound speed of the ultrasonic wave is fixed, the difference between theactual sound speed in the subject and the set sound speed often occurs.

If the set sound speed is different from the actual sound speed, it isnot possible to accurately perform the delay correction. As a result,there is a problem in that image quality of the ultrasound image isdeteriorated, for example, the produced ultrasound image is distortedwith respect to the actual subject.

In contrast, JP 2011-92686 A describes an ultrasound diagnosticapparatus in which regions of interest are set so as to divide theinside of the subject (ultrasound image) into a plurality of regions,and a sound speed is set for each of the regions of interest.Specifically, in this apparatus, the transmission and reception of anultrasonic wave for forming a transmission focus corresponding to aregion of interest is performed, delay correction or phasing addition isperformed by setting a plurality of sound speeds to calculate the focusindex (for example, sharpness or the like) of the region of interest,and the sound speed at which the highest focus index is obtained is setas the sound speed in the region of interest.

According to an ultrasound diagnostic apparatus described in JP2011-92686 A, an accurate sound speed is set corresponding to anindividual difference of the subject, each of the sites in the subject,or the like, and delay correction is performed, thereby producing ahigh-quality ultrasound image with no distortion or the like.

The sound speed of the subject changes depending on the state of atissue, such as a muscle. In addition, change in the position of theprobe causes change in the sound speed of the subject in a region withwhich the probe is in contact. Accordingly, in order to stably obtain anultrasound image of high-quality, it is desirable to appropriatelyupdate (reset) the sound speed.

On the other hand, in the ultrasound diagnostic apparatus, when settingthe sound speed, many operations are required. That is, a frequentupdate of the sound speed imposes a heavy burden on the ultrasounddiagnostic apparatus. For this reason, in the ultrasound diagnosticapparatus, the update of the sound speed is performed at a reasonableregular timing, for example, once at a predetermined time interval (oncefor every predetermined number of frames).

Meanwhile, as is well known, in the ultrasound diagnostic apparatus, inorder to favorably perform the observation of the ultrasound image,various instructions can be given to the ultrasound image displayed on adisplay.

For example, while the ultrasound image is basically a motion image,that is, a live image, in the ultrasound diagnostic apparatus, in orderto perform the observation of an intended site in detail, a FREEZEbutton (freeze switch) which instructs the display of a still image,instead of a motion image, is provided.

The ultrasound diagnostic apparatus is also provided with region ofinterest (ROI) setting means or observation depth setting means so as toinstruct an observation target range (observation region) of theultrasound image.

In addition, the ultrasound diagnostic apparatus is provided with gain(amplification and attenuation of the reception signal) adjustment meansso as to change image quality (luminance) of the ultrasound image. Anapparatus which can change image quality for each observation depth isalso known.

Moreover, the ultrasound image has various image modes. For example, theultrasound image has image modes such as a fundamental image mode inwhich according to a center frequency of an ultrasonic wave to bereceived, the center frequencies of ultrasonic waves to be transmittedand received are identical, a tissue harmonic mode in which anultrasonic echo of a harmonic of a transmitted ultrasonic wave isreceived to produce an ultrasound image, a compound harmonic mode inwhich an ultrasonic echo having the same center frequency as that of atransmitted ultrasonic wave and a harmonic of the transmitted ultrasonicwave are received to perform image synthesis, and the like, and theultrasound diagnostic apparatus is configured such that a desired modecan be selected and instructed.

Such various instructions (operations) are performed for some purpose.

For example, the instruction of freeze, the instruction to set an ROI,and the instruction to change an observation depth are made so as toobserve a specific region in the subject in more detail. The change ofimage quality or the change of the image mode is instructed so as toobserve an observation site in detail with an ultrasound image ofhigher-quality or an ultrasound image more suitable for the observation.

However, as described above, since a frequent update of the sound speedimposes a heavy burden on the ultrasound diagnostic apparatus, theupdate of the sound speed is performed at a reasonable regular timing.For this reason, in the ultrasound diagnostic apparatus, there are manycases where the sound speed which is set when various instructions areperformed is different from the actual sound speed of the subject.

As a result, in spite of an ultrasound image desired to be observed indetail, deterioration of image quality, such as distortion, may occur inthe displayed ultrasound image.

SUMMARY OF THE INVENTION

The present invention has been accomplished in order to solve thedrawbacks in the prior art, and an object thereof is to provide anultrasound diagnostic apparatus, a method of producing an ultrasoundimage, and a recording medium which can stably display an ultrasoundimage of high-quality even when various instructions, such as aninstruction of freeze, an instruction to change in an observation targetrange, an instruction to change image quality, an instruction to changean image mode, and the like are given in an ultrasound diagnosticapparatus.

In order to achieve such object, the present invention provides anultrasound diagnostic apparatus comprising: a piezoelectric elementarray which has piezoelectric elements arranged therein, eachpiezoelectric element configured to transmit an ultrasonic wave, toreceive an ultrasonic echo reflected by a subject, and to output areception signal according to a received ultrasonic wave; a controllerwhich controls ultrasonic transmission and reception by thepiezoelectric element array; a storage which stores the reception signaloutput from the piezoelectric element array; a sound speed setter whichsets a sound speed in the subject using the reception signal stored inthe storage; an image producer which processes the reception signaloutput from the piezoelectric element array or the reception signal readfrom the storage, based on the sound speed set by the sound speed setterto produce an ultrasound image; a display; and an operating device whichhas a freeze instruction inputter configured to instruct to display astill image on the display, an observation target range instructioninputter configured to specify an observation target range of anultrasound image displayed on the display, an image quality changeinstruction inputter configured to instruct to change image quality ofthe ultrasound image, and a mode change instruction inputter configuredto instruct to change an image mode of the ultrasound image, wherein:

the controller causes the piezoelectric element array to performultrasonic transmission and reception for sound speed setting so as toallow the sound speed setter to set the sound speed in response to atleast one instruction out of an instruction to display a still imagefrom the freeze instruction inputter, an instruction on the observationtarget range from the observation target range instruction inputter, aninstruction to change image quality from the image quality changeinstruction inputter, and an instruction to change an image mode fromthe mode change instruction inputter; the sound speed setter sets thesound speed in the subject using a reception signal obtained by theultrasonic transmission and reception for sound speed setting to updatethe sound speed; the image producer processes the reception signaloutput from the piezoelectric element array based on an updated soundspeed to produce an ultrasound image; and the display displays theultrasound image produced by processing based on the updated soundspeed.

In the inventive ultrasound diagnostic apparatus as such, it ispreferable that the controller causes the piezoelectric element array toperform the ultrasonic transmission and reception for sound speedsetting in response to any instruction out of the instruction to displaya still image from the freeze instruction inputter, the instruction onthe observation target range from the observation target rangeinstruction inputter, the instruction to change image quality from theimage quality change instruction inputter, and the instruction to changean image mode from the mode change instruction inputter.

Preferably, the controller causes the piezoelectric element array toperform the ultrasonic transmission and reception for sound speedsetting immediately after the instruction is given.

The sound speed setter preferably divides the subject into a pluralityof regions and sets the sound speed for each region, and the imageproducer preferably processes the reception signal based on the soundspeed set for each region to produce an ultrasound image.

It is preferable that the image producer processes the reception signalobtained by the ultrasonic transmission and reception for sound speedsetting based on the updated sound speed to produce an ultrasound imagein response to the instruction to display a still image from the freezeinstruction inputter.

It is also preferable that the image producer processes a receptionsignal output from the piezoelectric element array during ultrasonictransmission and reception before the ultrasonic transmission andreception for sound speed setting based on the updated sound speed toproduce an ultrasound image in response to the instruction to display astill image from the freeze instruction inputter.

Preferably, the image producer processes a reception signal output fromthe piezoelectric element array at least during ultrasonic transmissionand reception immediately before the ultrasonic transmission andreception for sound speed setting based on the updated sound speed toproduce an ultrasound image.

It is preferable that, in response to the instruction to display a stillimage from the freeze instruction inputter, the image producer processesa reception signal output from the piezoelectric element array duringultrasonic transmission and reception before the ultrasonic transmissionand reception for sound speed setting based on the updated sound speedto produce an ultrasound image after update of the sound speed, andprocesses the reception signal based on a sound speed set before theupdate of the sound speed to produce an ultrasound image before theupdate of the sound speed, and the display displays the ultrasound imageafter the update of the sound speed and the ultrasound image before theupdate of the sound speed.

Preferably, the operating device has a selection instruction inputterconfigured to select either the ultrasound image after the update of thesound speed or the ultrasound image before the update of the soundspeed, and, when selection is made by the selection instructioninputter, the display only displays the ultrasound image as selected.

The observation target range instruction inputter preferably includeseither or both of an observation depth change instruction inputterconfigured to instruct change in observation depth and a region ofinterest setting instruction inputter configured to instruct setting ofa region of interest.

It is preferable that the region of interest setting instructioninputter has a region of interest determination instruction inputterconfigured to instruct determination of a region of interest and, when aregion of interest is determined through the region of interestdetermination instruction inputter, the controller, considering that theinstruction on the observation target range is given, causes thepiezoelectric element array to perform the ultrasonic transmission andreception for sound speed setting.

It is also preferable that the region of interest setting instructioninputter has a region of interest movement instruction inputterconfigured to instruct movement of a region of interest and a region ofinterest size change instruction inputter configured to instruct changein size of a region of interest and, when no operation is performedthrough the region of interest movement instruction inputter or theregion of interest size change instruction inputter for a predeterminedtime in a state where the setting of a region of interest is instructed,the controller, considering that the instruction on the observationtarget range is given, causes the piezoelectric element array to performthe ultrasonic transmission and reception for sound speed setting.

It is preferable that the observation depth change instruction inputterhas an extension and reduction instruction inputter configured toincrease and decrease the observation depth, and the sound speed setterupdates the sound speed only for a region extended or reduced throughthe extension and reduction instruction inputter configured to increaseand decrease the observation depth.

It is preferable that, when the instruction on the observation targetrange is given by the observation target range instruction inputter, thecontroller causes the piezoelectric element array to perform theultrasonic transmission and reception for sound speed setting to form atransmission focus for sound speed setting corresponding to theobservation target range thus specified, and the sound speed setter setsand updates the sound speed in the subject according to the observationtarget range thus specified.

It is preferable that the image quality change instruction inputterinstructs to change image quality of the ultrasound image for apredetermined region and, when change in image quality for thepredetermined region is instructed by the image quality changeinstruction inputter, the controller causes the piezoelectric elementarray to perform, with respect to the predetermined region, theultrasonic transmission and reception for sound speed setting so as toallow the sound speed setter to set the sound speed, whereupon the soundspeed setter preferably sets a sound speed in the predetermined regionusing the reception signal obtained by the ultrasonic transmission andreception for sound speed setting to update the sound speed.

It is preferable that change in image quality of the ultrasound imageaccording to the instruction to change image quality from the imagequality change instruction inputter is performed by either or both ofchange of an amplification factor for amplifying the reception signaland image processing in the image producer.

Preferably, the image quality change instruction inputter has a functionof instructing the change in image quality for each depth region set inadvance and, when a depth region for which image quality is to bechanged is specified by an instruction from the image quality changeinstruction inputter, the sound speed setter only updates the soundspeed in the specified depth region.

It is also preferable that the image quality change instruction inputterhas at least one of a gain adjustment instruction inputter configured toadjust gain of an ultrasound image, a dynamic range adjustmentinstruction inputter configured to adjust dynamic range of an ultrasoundimage, a gradation curve processing instruction inputter configured toprocess gradation curve of an ultrasound image, a sharpness adjustmentinstruction inputter configured to adjust sharpness of an ultrasoundimage, and a speckle noise removal processing instruction inputterconfigured to instruct removal of speckle noise from an ultrasoundimage.

The image mode is preferably any of a fundamental wave mode, a tissueharmonic mode, and a compound harmonic mode.

The image producer preferably processes the reception signal obtained bythe ultrasonic transmission and reception for sound speed setting basedon the updated sound speed to produce an ultrasound image.

The present invention also provides a method of producing an ultrasoundimage, the method comprising the steps of: performing ultrasonictransmission and reception for sound speed setting so as to set a soundspeed in a subject in response to at least one instruction out of aninstruction to freeze to display a still image, an instruction on anobservation target range of an ultrasound image, an instruction tochange image quality of an ultrasound image, and an instruction tochange an image mode of an ultrasound image; setting the sound speed inthe subject using a reception signal obtained by the ultrasonictransmission and reception for sound speed setting; processing anultrasonic reception signal based on the sound speed to produce anultrasound image; and displaying the ultrasound image.

In the inventive method of producing an ultrasound image as such, it ispreferable that, if any instruction out of the instruction to freeze todisplay a still image, the instruction on an observation target range ofan ultrasound image, the instruction to change image quality of anultrasound image, and the instruction to change an image mode of anultrasound image is given, the ultrasonic transmission and reception forsound speed setting is performed and the sound speed in the subject isset.

The ultrasonic transmission and reception for sound speed setting ispreferably performed immediately after the instruction is given, so asto set the sound speed in the subject.

Preferably, the sound speed is set for each region obtained by dividingthe subject into a plurality of regions, and the ultrasound image isproduced based on the sound speed set for each region.

The present invention also provides a recording medium having recordedthereon a program for making an ultrasound diagnostic apparatus displayan ultrasound image, the program causing a computer to execute: atransmission and reception step of performing ultrasonic transmissionand reception for sound speed setting so as to set a sound speed in asubject in response to at least one instruction out of an instruction tofreeze to display a still image, an instruction on an observation targetrange of an ultrasound image, an instruction to change image quality ofan ultrasound image, and an instruction to change an image mode of anultrasound image; a sound speed setting step of setting the sound speedin the subject using a reception signal obtained in the transmission andreception step; an image production step of processing an ultrasonicreception signal based on the sound speed set in the sound speed settingstep to produce an ultrasound image; and a display step of displayingthe ultrasound image produced in the image production step on a display.

In the inventive recording medium as such, it is preferable that, in thetransmission and reception step of the program, the ultrasonictransmission and reception for sound speed setting is performed inresponse to any instruction out of the instruction to freeze to displaya still image, the instruction on an observation target range of anultrasound image, the instruction to change image quality of anultrasound image, and the instruction to change an image mode of anultrasound image.

Preferably, in the transmission and reception step of the program, theultrasonic transmission and reception for sound speed setting isperformed immediately after the instruction is given.

The program is preferably such that, in the sound speed setting step,the sound speed is set for each region obtained by dividing the subjectinto a plurality of regions, and in the image production step, theultrasound image is produced based on the sound speed set for eachregion.

According to the invention, in an ultrasound diagnostic apparatus, thesound speed of the subject is updated in accordance with an instructionto display a still image by a FREEZE button; an instruction of anobservation target range, such as ROI setting or change in observationdepth; an instruction to change image quality, such as gain adjustment;an instruction to change an image mode such as change from a fundamentalimage mode, in which the center frequencies of ultrasonic waves to betransmitted and received are identical, to a tissue harmonic mode; orthe like, and an ultrasound image is produced using the updated soundspeed.

Therefore, according to the present invention, it is possible to displayan ultrasound image of high-quality based on an accurate sound speedcorresponding to various instructions in terms of an ultrasound imagedesired to be observed in detail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram conceptually showing an ultrasound diagnosticapparatus of the invention.

FIG. 2 is a diagram conceptually showing an example of an operatingdevice of the ultrasound diagnostic apparatus shown in FIG. 1.

FIGS. 3A and 3B are conceptual diagrams illustrating transmission andreception of ultrasonic waves in the ultrasound diagnostic apparatusshown in FIG. 1.

FIG. 4 is a conceptual diagram illustrating an example of update of asound speed in the ultrasound diagnostic apparatus shown in FIG. 1.

FIG. 5 is a conceptual diagram illustrating another example of update ofa sound speed in the ultrasound diagnostic apparatus shown in FIG. 1.

FIGS. 6A and 6B are conceptual diagrams illustrating another example ofupdate of a sound speed in the ultrasound diagnostic apparatus shown inFIG. 1.

FIGS. 7A and 7B are conceptual diagrams illustrating another example ofupdate of a sound speed in the ultrasound diagnostic apparatus shown inFIG. 1.

FIGS. 8A and 8B are conceptual diagrams illustrating another example ofupdate of a sound speed in the ultrasound diagnostic apparatus shown inFIG. 1.

FIGS. 9A to 9C are conceptual diagrams illustrating another example ofupdate of a sound speed in the ultrasound diagnostic apparatus shown inFIG. 1.

FIGS. 10A and 10B are conceptual diagrams illustrating another exampleof update of a sound speed in the ultrasound diagnostic apparatus shownin FIG. 1.

FIGS. 11A and 11B are conceptual diagrams illustrating another exampleof update of a sound speed in the ultrasound diagnostic apparatus shownin FIG. 1.

FIGS. 12A and 12B are conceptual diagrams illustrating another exampleof update of a sound speed in the ultrasound diagnostic apparatus shownin FIG. 1.

FIGS. 13A and 13B are conceptual diagrams illustrating another exampleof update of a sound speed in the ultrasound diagnostic apparatus shownin FIG. 1.

FIGS. 14A and 14B are conceptual diagrams illustrating an example of animage mode in the ultrasound diagnostic apparatus shown in FIG. 1.

FIGS. 15A to 15D are conceptual diagrams illustrating another example ofupdate of a sound speed in the ultrasound diagnostic apparatus shown inFIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an ultrasound diagnostic apparatus, a method of producingan ultrasound image, and a recording medium of the invention will bedescribed in detail on the basis of preferred examples described in theaccompanying drawings.

FIG. 1 is a block diagram conceptually showing an example of anultrasound diagnostic apparatus of the invention which executes a methodof producing an ultrasound image of the invention.

As shown in FIG. 1, an ultrasound diagnostic apparatus 10 has anultrasound probe 12 (hereinafter, referred to as a probe 12) whichincludes a piezoelectric element array 14.

A transmission circuit 16 and a reception circuit 18 are connected tothe piezoelectric element array 14 of the probe 12. A signal processor20, a digital scan converter (DSC) 24, an image processor 26, a displaycontroller 28, and a display unit 30 are sequentially connected to thereception circuit 18. An image memory 32 is connected to the imageprocessor 26.

An ultrasound image producer 50 is constituted by the signal processor20, the DSC 24, the image processor 26, and the image memory 32.

A reception data memory 36 is connected to the reception circuit 18 andthe signal processor 20, and a sound speed setter 40 is connected to theimage memory 32 and the signal processor 20.

Further, a controller 42 is connected to the transmission circuit 16,the reception circuit 18, the signal processor 20, the DSC 24, thedisplay controller 28, the reception data memory 36, and the sound speedsetter 40. An operating device 46 and a storage unit 48 are connected tothe controller 42.

In the illustrated example, the transmission circuit 16, the receptioncircuit 18, the ultrasound image producer 50, the display controller 28,the display unit 30, the reception data memory 36, the sound speedsetter 40, the controller 42, the operating device 46, and the storageunit 48 constitute a diagnostic apparatus body of the ultrasounddiagnostic apparatus 10.

The diagnostic apparatus body is constituted using, for example, acomputer or the like.

The piezoelectric element array 14 has a plurality of piezoelectricelements (ultrasound transducers) arranged in a one-dimensional ortwo-dimensional manner. Each of the piezoelectric elements transmits anultrasonic wave in accordance with a driving signal supplied from thetransmission circuit 16, receives an ultrasonic echo from a subject, andoutputs a reception signal.

The piezoelectric element is constituted by a vibrator in whichelectrodes are formed at both ends of a piezoelectric substance.Examples of the piezoelectric substance include piezoelectric ceramicrepresented by PZT (lead zirconate titanate), a polymer piezoelectricelement represented by PVDF (polyvinylidene difluoride), piezoelectricsingle crystal represented by PMN-PT (lead magnesium niobate-leadtitanate solid solution), and the like.

If a pulsed or continuous-wave voltage is applied across the electrodesof the vibrator, the piezoelectric substance expands and contracts,whereby pulsed or continuous-wave ultrasonic waves are produced from therespective vibrators, and the ultrasonic waves are synthesized to forman ultrasonic beam.

When receiving the ultrasonic waves, the vibrators expand and contractto produce electric signals. The electric signals are output from therespective piezoelectric elements of the piezoelectric element array 14as the reception signals of the ultrasonic waves.

The transmission circuit 16 includes, for example, a plurality of pulsegenerators. The transmission circuit 16 adjusts the delay amount of eachof the driving signals on the basis of a transmission delay patternselected in accordance with a control signal from the controller 42 suchthat the ultrasonic waves transmitted from the piezoelectric elementarray 14 form an intended ultrasonic beam, and supplies the drivingsignals to a plurality of piezoelectric elements.

The reception circuit 18 has a plurality of amplifiers and A/Dconverters, and the like. The reception circuit 18 amplifies and A/Dconverts the reception signals transmitted from the respectivepiezoelectric elements of the piezoelectric element array 14, andproduces digitized reception data corresponding to the number ofreception channels.

The amplifier of the reception circuit 18 may perform gain adjustment(brightness adjustment) of an ultrasound image according to operation ofan STC key 68 or a GAIN dial 114 described later, in addition to apredetermined amplification of reception signal. At this time, theamplifier of the reception circuit 18 changes the overall amplificationfactor (gain) in accordance with operation of the GAIN dial 114, andchanges the amplification factor in a corresponding depth region (thatis, reception time) in accordance with operation of the STC key 68.

Here, under the control by the controller 42 described later, thetransmission circuit 16 and the reception circuit 18 cause thepiezoelectric element array 14 to perform transmission and reception ofan ultrasonic wave for sound speed setting for allowing the sound speedsetter 40 to set the sound speed of an ultrasonic wave in the subject ata predetermined timing, for example, once for every predetermined numberof frames.

If an instruction of freeze by a FREEZE button 116 provided in theoperating device 46, an instruction of gain adjustment by the GAIN dial114, or the like is performed similarly under the control by thecontroller 42, the transmission circuit 16 and the reception circuit 18cause the piezoelectric element array 14 to perform transmission andreception of an ultrasonic wave for sound speed setting for allowing thesound speed setter 40 to set a sound speed in a subsequent frame(preferably, a frame immediately after the instruction).

In this regard, detailed description will be provided later.

The signal processor 20 carries out delay correction on reception dataproduced by the reception circuit 18 on the basis of the sound speed (aset sound speed and an optimum sound speed described later) input fromthe sound speed setter 40 to produce delay correction data. Then, thesignal processor 20 performs reception focusing processing by addingdelay correction data (phasing addition). With this processing, thefocus of the ultrasonic echo is narrowed to produce a sound ray signal(sound ray data).

Further, the signal processor 20 performs correction of attenuation dueto distance in accordance with the depth of the reflection point of theultrasonic wave on the sound ray signal, and then performs envelopedetection processing to produce a B-mode image signal (ultrasound image)which is tomographic image information relating to the tissue in thesubject.

The signal processor 20 may perform the gain adjustment of theultrasound image according to operation of the STC key 68 or the GAINdial 114 described later.

The DSC 24 converts (raster-converts) the B-mode image signal producedby the signal processor 20 to an image signal based on a normaltelevision signal scanning system.

The image processor 26 performs various kinds of necessary imageprocessing, such as gradation processing, on the B-mode image signalinput from the DSC 24, and then outputs the B-mode image signalsubjected to image processing to the display controller 28.Alternatively, the image processor 26 stores the B-mode image signalsubjected to the similar image processing in the image memory 32. Theimage processor 26 may perform the gain adjustment of the ultrasoundimage according to operation of the STC key 68 or the GAIN dial 114described later. That is, in the ultrasound diagnostic apparatus 10, thegain adjustment of the ultrasound image according to operation of theSTC key 68 or the GAIN dial 114 may be performed by at least one ofadjustment of the amplification factor in the amplifier of the receptioncircuit 18, image processing in the signal processor 20, and imageprocessing in the image processor 26. The gain adjustment of theultrasound image by image processing may be performed by a known method.

As described above, the ultrasound image producer 50 is constituted bythe signal processor 20, the DSC 24, the image processor 26, and theimage memory 32.

The display controller 28 controls the display unit 30 to display theultrasound image or the like on the basis of the B-mode image signalsubjected to image processing in the image processor 26 or various kindsof information input by the operating device 46.

The display unit 30 includes, for example, a display, such as an LCD,and displays the ultrasound image under the control of the displaycontroller 28.

The reception data memory 36 sequentially stores reception data outputfrom the reception circuit 18, and also stores delay correction dataproduced in the signal processor 20.

The sound speed setter 40 sets the sound speed (optimum sound speeddescribed later) of the ultrasonic wave in the subject.

In the present invention, as an example, the sound speed setter 40 givesa predetermined set sound speed to the signal processor 20, and changesthe set sound speed to cause the ultrasound image producer 50 to producethe B-mode image signal. Then, the sound speed setter 40 analyzes eachB-mode image produced at each set sound speed, and sets a sound speedwhich gives maximum contrast or sharpness to the image as the optimumsound speed of the subject. The sound speed setter 40 divides the insideof the subject into a plurality of regions, and sets the optimum soundspeed for each region.

The controller 42 controls respective components of the ultrasounddiagnostic apparatus on the basis of a command input from the operatingdevice 46 by an operator (physician).

The controller 42 gives an instruction to the transmission circuit 16and the reception circuit 18 so that the piezoelectric element array 14transmits an intended ultrasonic beam, receives an ultrasonic echo bythe ultrasonic beam, and outputs a reception signal.

The storage unit 48 stores an operation program or the like, and arecording medium, such as a hard disk, a flexible disk, an MO, an MT, aRAM, a CD-ROM, a DVD-ROM, an SD card, a CF card, or a USB memory, aserver, or the like may be used.

Although the signal processor 20, the DSC 24, the image processor 26,the display controller 28, and the sound speed setter 40 are constitutedby a CPU and an operation program which causes the CPU to performvarious kinds of processing, these may be constituted by digitalcircuits.

The operating device 46 is used when the operator performs inputoperation, and similarly to that for the known ultrasound diagnosticapparatus, has means for instructing freeze (display of a still image)(freeze instruction inputter), switching means of a display mode, suchas a B mode or an M mode, adjustment means of image quality (imagequality adjustment instruction inputter), setting means of a region ofinterest (ROI) (region of interest (ROI) setting instruction inputter),and the like.

FIG. 2 conceptually shows an example of the operating device 46 (a partthereof).

In the apparatus of the illustrated example, the operating device 46 isprovided with a power switch 60 and a touch panel 62 for performingvarious kinds of display and input operation.

Reference numeral 64 denotes a menu button.

The menu button 64 is operating means (operating unit) which displaysmenus for calling various functions on the touch panel 62. In theillustrated example, as an example, four menus of image adjustment,preset, patient information, and system tool are set.

Reference numeral 68 denotes an STC key (attenuation correction key).The STC key 68 is operating means (operating unit) for performing gainadjustment (amplification and attenuation) of each depth of theultrasound image, that is, luminance adjustment of each depth of theultrasound image. In the illustrated example, gain adjustment can beperformed individually at six depths.

That is, the STC key 68 is an image quality change instruction inputteraccording to the invention.

Reference numeral 70 denotes a patient information button. The patientinformation button 70 is operating means (operating unit) for displayingpatient information on the display unit 30.

Reference numeral 72 denotes a menu control switch. The menu controlswitch 72 is used to perform operation of each menu displayed on thetouch panel 62 by the menu button 64, and in the illustrated example,four operating means (operating units) are set.

Reference numeral 74 denotes an OPTIMIZE button. The OPTIMIZE button 74is operating means (operating unit) which enables an automaticattenuation correction and sound speed correction function.

Reference numeral 76 denotes a function button. The function button 76is operating means (operating unit) in which an examiner can arbitrarilyset the function of the button by a system setting function.

Reference numeral 78 denotes a COMPOUND button.

The COMPOUND button 78 is operating means (operating unit) which startsand stops a compound harmonic mode (hereinafter, also referred to as aCH mode) in which an ultrasonic echo having the same center frequency asthe transmitted ultrasonic wave (hereinafter, also referred to as afundamental wave) and an ultrasonic echo of a harmonic of thefundamental wave are received and synthesized, thereby reducing specklenoise.

In the illustrated example, if the COMPOUND button 78 is pressed in astate where display in a different image mode is performed, the imagemode is transited to the CH mode. If the COMPOUND button 78 is pressedin a state where display in the CH mode is performed, the image mode istransited to a fundamental image mode (hereinafter, also referred to asa fundamental wave mode) in which an ultrasonic echo having the samecenter frequency as a fundamental wave is received.

Reference numeral 80 denotes a HARMONICS button. The HARMONICS button 80is operating means (operating unit) which starts and stops a tissueharmonic mode (hereinafter, also referred to as a THI mode) in which anultrasonic echo of a harmonic of a fundamental wave is received and anultrasound image is produced.

In the illustrated example, if the HARMONICS button 80 is pressed in astate where display in a different image mode is performed, the imagemode is transited to the THI mode. If the HARMONICS button 80 is pressedin a state where display in the THI mode is performed, the image mode istransited to the fundamental wave mode.

That is, the COMPOUND button 78 and the HARMONICS button 80 are each amode change instruction inputter according to the invention.

Reference numeral 82 denotes a ZOOM button. The ZOOM button 82 isoperating means (operating unit) which starts an enlargement(zooming-in) function of the ultrasound image displayed on the displayunit 30.

Reference numeral 84 denotes a dual mode selector switch. The dual modeselector switch 84 is operating means (operating unit) which switches anoperable image when ultrasound diagnosis in a dual mode such as a B/Cmode is performed.

Reference numerals 86 to 94 denote display mode selection means (displaymode switching means). That is, these means are each the mode changeinstruction inputter of the invention.

Reference numeral 86 denotes a PW button. The PW button 86 is operatingmeans (operating unit) which starts and stops a pulse Doppler mode.

Reference numeral 90 denotes a C button. The C button 90 is operatingmeans (operating unit) which starts and stops a color Doppler mode.

Reference numeral 92 denotes an M button. The M button 92 is operatingmeans (operating unit) which starts and stops an M mode.

Reference numeral 94 denotes a B button. The B button 94 is operatingmeans (operating unit) which starts and stops a B mode.

Reference numeral 96 denotes a BODY PATTERN button. The BODY PATTERNbutton 96 is operating means (operating unit) which is used to display abody pattern, that is, a graphic pattern representing a site to beimaged.

Reference numeral 98 denotes a CINE button. The CINE button 98 isoperating means (operating unit) which is used to replay and stop amotion image clip.

Reference numeral 100 denotes a DELETE button. The DELETE button 100 isoperating means (operating unit) which is used to return to a previousprocess during measurement so as to restart the measurement.

Reference numeral 102 denotes a trackball. The trackball 102 isoperating means (operating unit) which is used to perform movement of acursor, determination of the size or position of a region of interest(ROI), arrangement of a measurement tool, redisplay of a motion imageclip, and the like. The trackball 102 constitutes a part of an ROIsetting instruction inputter, that is, a part of the observation targetrange instruction inputter in the invention.

The operating device 46 of the ultrasound diagnostic apparatus of theinvention may use a so-called track pad (touch pad), instead of thetrackball.

Reference numeral 104 denotes a MEASURE button. The MEASURE button 104is operating means (operating unit) which starts a dynamic caliper, acalculation menu, or a Doppler waveform autotracing function.

Reference numeral 106 denotes a SET button. The SET button 106 isoperating means (operating unit) which is used to select (determine) theitem or function on the screen of the display unit 30.

In the ultrasound diagnostic apparatus 10, as an example, the ROI isdetermined by pressing the SET button 106. That is, the SET button 106constitutes a part of the observation target range instruction inputterin the invention.

Reference numeral 108 denotes a DEPTH button. The DEPTH button 108 isoperating means (operating unit) which is used to change (increase anddecrease) the observation depth of the ultrasound image. That is, theDEPTH button 108 is an observation target range instruction inputteraccording to the invention.

Reference numeral 110 denotes a STORE button. The STORE button 110 isoperating means (operating unit) which is used to store an imagedisplayed on the display unit 30 in a device set in advance or print theimage.

Reference numeral 112 denotes an encoder dial. The encoder dial 112 isoperating means (operating unit) which is used to adjust a Doppler anglein the pulse Doppler mode or to rotate the mark of the probe at the timeof body pattern display.

Reference numeral 114 denotes a GAIN dial. The GAIN dial 114 isoperating means (operating unit) which is used to adjust a gain(luminance of an ultrasound image) in the B mode, the M mode, the colorDoppler mode, and the pulse Doppler mode. That is, the GAIN dial 114 isan image quality change instruction inputter according to the invention.

Reference numeral 116 denotes a FREEZE button (freeze switch). TheFREEZE button 116 is operating means (operating unit) which is used toswitch between a live mode, in which a motion image (live image) of anultrasound image is displayed at a predetermined frame rate, and afreeze mode, in which a still image (freeze image) of an ultrasoundimage is displayed. That is, the FREEZE button 116 is the freezeinstruction inputter of the invention which instructs display of a stillimage (freeze image).

In the illustrated example, the FREEZE button 116 is arranged in thecenter of the GAIN dial 114.

Hereinafter, the invention will be described in more detail whiledescribing the action of the ultrasound diagnostic apparatus 10. Therecording medium of the invention is a computer-readable recordingmedium having recorded thereon a program which causes a computer toexecute a method of producing an ultrasound image described below.

As described above, in the ultrasound diagnostic apparatus 10, as anexample, the sound speed (optimum sound speed) of the ultrasonic wave inthe subject is updated (reset) once for every predetermined number offrames.

In addition, in the ultrasound diagnostic apparatus 10, when aninstruction of freeze is given by the above-described FREEZE button 116,when an instruction of ROI setting is given using the trackball 102 orthe like, when an instruction to change an observation depth is given bythe DEPTH button 108, when an instruction to change a gain is given bythe STC key 68 or the GAIN dial 114, and when an instruction to changean image mode is given by the COMPOUND button 78 or the HARMONICS button80 (further, by the B button 94 or the like), the optimum sound speed isupdated.

In the ultrasound diagnostic apparatus 10, the subject (an ultrasoundimage to be produced) is divided into a plurality of regions, and theoptimum sound speed is updated (set) for each region.

The update of the optimum sound speed is performed by transmission andreception of an ultrasonic wave for sound speed setting (“transmissionand reception of an ultrasonic wave” being hereafter also referred to as“ultrasonic transmission and reception” or simply as “transmission andreception”). The transmission and reception for sound speed setting istransmission and reception in which a transmission focus for sound speedsetting is formed by forming a transmission focus with higher densitythan transmission and reception for producing a B-mode image in one scanline (sound ray signal to be produced, namely, ultrasonic beam to beproduced).

FIG. 3A conceptually shows transmission and reception for producing aB-mode image (hereinafter, also referred to as normal transmission andreception), and FIG. 3B conceptually shows transmission and receptionfor sound speed setting.

In FIGS. 3A and 3B, the vertical direction is a depth direction (thetransmission and reception direction of the ultrasonic wave), and theupper side in the drawing is a shallower side (piezoelectric elementarray 14 side). The horizontal direction is an azimuth direction (thearrangement direction of the piezoelectric elements in the piezoelectricelement array 14).

In FIGS. 3A and 3B, a solid line which extends in the depth direction isa scan line. The position in the azimuth direction of each scan line inthe normal transmission and reception of FIG. 3A and the position in theazimuth direction of each scan line in the transmission and receptionfor sound speed setting of FIG. 3B coincide with each other.

In FIG. 3A, a white circle on the scan line is the transmission focus inthe normal transmission and reception. Meanwhile, in FIG. 3B, a blackcircle on the scan line is the transmission focus for sound speedsetting (hereinafter, also referred to as a focus for setting).

As shown in FIG. 3, in this example, in the normal transmission andreception, three transmission focuses (three positions of thetransmission focus in the depth direction) are defined for one scanline. That is, in the normal transmission and reception, threetransmissions and receptions having different transmission focuses areperformed for one scan line.

In contrast, in the transmission and reception for sound speed setting,five transmission focuses, that is, five focuses for setting are definedfor one scan line. That is, in the transmission and reception for soundspeed setting, five transmissions and receptions having differenttransmission focuses are performed for one scan line.

The regions in which the optimum sound speed is set are set by dividingthe subject parallel to the azimuth direction and the depth directioninto the form of a lattice, with each region centering at the focus forsetting.

That is, the optimum sound speed is set correspondingly to each focusfor setting.

In the ultrasound diagnostic apparatus 10 of the invention, the regionsof the subject, that is, the focuses for setting in the transmission andreception for sound speed setting may be appropriately set in accordancewith required image quality, the frame rate of an ultrasound image to bedisplayed, the arithmetic capacity (processing speed) of the ultrasounddiagnostic apparatus 10, or the like.

Preferably, the focus for setting is produced at the identical positionscorresponding to all pixels of an ultrasound image to be produced.Alternatively, one transmission focus may be set for every number ofpixels set appropriately, for example, one for every three pixels of anultrasound image, one for every nine pixels thereof, or the like.Alternatively, an ultrasound image may be divided into a specifiednumber of equal regions, for example, 10 or 20 equal regions, with thenumber being appropriately specified.

Further, the number of regions, the number of focuses for setting on onescan line, and the like may be set by the operator. The number ofregions, the number of focuses for setting, and the like may be set bymode selection or the like.

In the invention, the focus for setting may not necessarily be formedcorrespondingly to all regions. For example, a region including no focusfor setting may be set, and in regard to this region, the optimum soundspeed may be set by interpolation using the optimum sound speed set in aregion including a focus for setting.

In the normal transmission and reception and the transmission andreception for sound speed setting, the number of scan lines in one frameand the number of focuses on one scan line are not limited to theexample shown in FIGS. 3A and 3B. For example, in the normaltransmission and reception, one scan line may be formed with onetransmission focus (single transmission and reception), instead of threetransmission focuses (three transmissions and receptions). That is, inthe invention, in the normal transmission and reception and thetransmission and reception for sound speed setting, any number oftransmission focuses per scan line will do as long as the transmissionand reception for sound speed setting is higher in number oftransmission focuses (number of times of transmission and reception) perscan line.

Further, although the transmission and reception for sound speed settingonly has a larger number of transmission focuses on one scan line thanthe normal transmission and reception in the example shown in FIGS. 3Aand 3B, the transmission and reception for sound speed setting may havea larger number of scan lines than the normal transmission and receptionas necessary.

As described above, in the transmission and reception for sound speedsetting, five transmissions and receptions of an ultrasonic wave areperformed so that five focuses for setting are formed on one scan line.When updating the optimum sound speed, the controller 42 gives aninstruction to the transmission circuit 16 and the reception circuit 18so that the piezoelectric element array 14 transmits an ultrasonic beamwhich forms an intended transmission focus, and receives an ultrasonicecho by the ultrasonic beam.

The reception signals output from the respective piezoelectric elementsof the piezoelectric element array 14 by the transmission and receptionfor sound speed setting are subjected to amplification and A/Dconversion by the reception circuit 18 to produce reception data, andreception data is sequentially stored in the reception data memory 36.

When reception data by the transmission and reception for sound speedsetting is stored in the reception data memory 36, the sound speedsetter 40 supplies a first set sound speed S1 to the signal processor20.

The signal processor 20 reads reception data by the transmission andreception for sound speed setting from the reception data memory 36, andperforms delay correction on reception data on the basis of the suppliedset sound speed S1 to produce delay data. In addition, the signalprocessor 20 performs the reception focusing processing by adding theproduced delay data to produce a sound ray signal. Further, the signalprocessor 20 performs attenuation correction and envelope detectionprocessing on the sound ray signal to produce a B-mode image signalbased on the first set sound speed S1.

The B-mode image signal is raster-converted in the DSC 24, is subjectedto various kinds of image processing in the image processor 26, and isthen stored in the image memory 32 as a B-mode image signal for soundspeed setting based on the first set sound speed S1.

If the B-mode image signal corresponding to the first set sound speed S1given from the sound speed setter 40 is stored in the image memory 32,the sound speed setter 40 supplies a second set sound speed S2, thevalue of which changes from the first set sound speed S1 by apredetermined amount, to the signal processor 20. Thereafter, a B-modeimage for sound speed setting based on the second set sound speed S2 isformed and stored in the image memory 32 in a similar way as describedabove.

In this way, a plurality of set sound speeds S1 to Sn are sequentiallygiven from the sound speed setter 40 to the signal processor 20, and theB-mode image signals based on the set sound speeds S1 to Sn are producedby the ultrasound image producer 50 and stored in the image memory 32 asB-mode image signals for sound speed setting.

If the B-mode image signals, which are produced by the transmission andreception for sound speed setting and are based on the set sound speedsS1 to Sn, are stored in the image memory 32, the sound speed setter 40analyzes each B-mode image signal. Using the analysis result, the soundspeed setter 40 sets a sound speed which gives maximum image contrast orsharpness to the image as an optimum sound speed of the subject from theset sound speeds S1 to Sn, and supplies the optimum sound speed to thesignal processor 20.

The signal processor 20 to which the newly set optimum sound speed issupplied updates the optimum sound speed to the newly supplied optimumsound speed.

The analysis of the B-mode image signal and the setting of the optimumsound speed are performed for each region, that is, for each focus forsetting. That is, the sound speed which gives maximum image contrast orsharpness to the image is selected for each region and set as theoptimum sound speed of each region.

That is, the optimum sound speed is a sound speed inside the subjectbetween the region and the piezoelectric element on the supposition thatthe subject from the region to the piezoelectric element is uniform. Inother words, the optimum sound speed is an average sound speed insidethe subject from the region to the piezoelectric element.

A method of setting a sound speed in the subject is not limited to thismethod, and various known sound speed setting methods which are executedby the conventional ultrasound diagnostic apparatus or ultrasound imageproduction method can be used.

Meanwhile, in the ultrasound diagnostic apparatus 10, in the normaltransmission and reception, as conceptually shown in FIG. 3A, threetransmissions and receptions having different transmission focuses areperformed for one scan line. The controller 42 gives an instruction tothe transmission circuit 16 and the reception circuit 18 so that thepiezoelectric element array 14 transmits an ultrasonic beam which formsan intended transmission focus and receives an ultrasonic echo by theultrasonic beam.

The reception signals output from the respective piezoelectric elementsof the piezoelectric element array 14 by the normal transmission andreception are subjected to amplification and A/D conversion in thereception circuit 18 to produce reception data, and reception data issequentially stored in the reception data memory 36.

If reception data is stored in the reception data memory 36, the signalprocessor 20 reads reception data and performs delay correction on thebasis of the optimum sound speed set ahead to produce delay data. Then,the signal processor 20 performs reception focusing processing by addingthe produced delay data to produce a sound ray signal. Further, thesignal processor 20 performs attenuation correction and envelopedetection processing on the sound ray signal to produce a B-mode imagesignal. Alternatively, reception data may be supplied directly from thereception circuit 18 to the signal processor 20.

The B-mode image signal is raster-converted in the DSC 24, is subjectedto various kinds of image processing in the image processor 26, and isthen stored in the image memory 32 as a B-mode image signal.

The B-mode image signal processed by the image processor 26 is sent tothe display controller 28, and the B-mode image, information of thesubject, or the like is displayed on the display unit 30.

In the live mode, the normal transmission and reception shown in FIG. 3Ais performed repeatedly in accordance with a predetermined frame rate,the above-described processing is sequentially performed on thereception signal output from the piezoelectric element array 14, and amotion image of the B-mode image is displayed at the predetermined framerate.

Here, in the ultrasound diagnostic apparatus 10, it is assumed that in astate where the normal transmission and reception shown in FIG. 3A isperformed at a predetermined frame rate, and a motion image in the livemode is displayed, the FREEZE button 116 is operated, and freeze isinstructed (display of a still image is instructed (that is, switchingto the freeze mode is instructed)). If freeze is instructed, thecontroller 42 gives an instruction to the transmission circuit 16 andthe reception circuit 18 so that the piezoelectric element array 14performs the transmission and reception for sound speed setting shown inFIG. 3B in transmission and reception immediately after freeze isinstructed, and as described above, the sound speed setter 40 sets theoptimum sound speed and updates the optimum sound speed.

As conceptually shown in FIG. 4, when a frame in which the sound speedis last updated (set) is a zero-th frame, if the FREEZE button 116 isoperated in the N-th frame and freeze is instructed, the transmissionand reception for sound speed setting shown in FIG. 3B is performed inthe (N+1)th frame which is a frame immediately after the instruction offreeze.

In the invention, the transmission and reception for sound speed settingmay be performed in a frame after the frame immediately after theinstruction of freeze or the instruction described below such as aninstruction of an observation target range, an instruction to changeimage quality, an instruction to change an image mode, or the like isperformed. That is, the transmission and reception for sound speedsetting may be performed not in the (N+1)th frame, but in the (N+2)thframe or a frame after the (N+2)th frame.

However, it is preferable that the transmission and reception for soundspeed setting be performed in the frame ((N+1)th frame) immediatelyafter the instruction of freeze or the instruction described below suchas an instruction of an observation target range, an instruction tochange image quality, an instruction to change an image mode, or thelike is performed. Accordingly, the update of the sound speed canrapidly be performed in response to various instructions (operations),whereby the enhancement of the quality of an ultrasound image desired bythe operator can be performed more rapidly.

In particular, in regard to the instruction of freeze, the operatorwants to see a still image at time point when freeze is performed. Forthis reason, it is preferable that, after freeze is instructed, thetransmission and reception for sound speed setting be performed in aframe immediately after the freeze instruction by the FREEZE button 116.

After the transmission and reception for sound speed setting isperformed in the (N+1)th frame, as described above, reception datathereof is stored in the reception data memory 36, the signal processor20 reads reception data from the reception data memory 36, and theoptimum sound speed is set by the sound speed setter 40.

The sound speed setter 40 supplies the newly set optimum sound speed tothe signal processor 20, and the signal processor 20 updates the optimumsound speed. That is, in the ultrasound diagnostic apparatus 10, as apreferred embodiment, the transmission and reception for sound speedsetting is performed immediately after freeze is instructed, and theoptimum sound speed is updated.

After the optimum sound speed is updated, the signal processor 20 readsreception data by the transmission and reception for sound speed settingin the (N+1)th frame from the reception data memory 36 again, andperforms delay correction on the basis of the updated optimum soundspeed to produce a B-mode image signal. When producing the B-mode imagesignal, thinning or the like of reception data may be performed asnecessary.

The B-mode image signal in the (N+1)th frame produced by the signalprocessor 20 is processed by the DSC 24 and the image processor 26, andis displayed on the display unit 30 as a still image according to thefreeze instruction.

As described above, according to the invention, in the ultrasounddiagnostic apparatus, a still image according to the instruction offreeze is produced and displayed by performing the transmission andreception for sound speed setting immediately after the instruction offreeze to update the sound speed and producing an ultrasound image onthe basis of the updated sound speed.

Therefore, according to the invention, it is possible to produce a stillimage according to the instruction of freeze at an accurate sound speed,and to make a still image of an ultrasound image desired to be observedin detail a high-quality ultrasound image with no image qualitydeterioration due to distortion or the like.

In the invention, the B-mode image may be produced using reception dataobtained by the normal transmission and reception in the N-th frame inwhich freeze is instructed.

In this case, reception data by at least the most recent normaltransmission and reception is constantly stored in the reception datamemory 36.

In the ultrasound diagnostic apparatus 10, as shown in FIG. 4, in astate where the normal transmission and reception shown in FIG. 3A isrepeatedly performed at a predetermined frame rate, and a motion imagein the live mode is displayed, if freeze is instructed in the N-th frameby the FREEZE button 116, as described above, the transmission andreception for sound speed setting is performed in the subsequent (N+1)thframe to update the optimum sound speed.

After the optimum sound speed is updated, the signal processor 20 readsreception data in the N-th frame from the reception data memory 36 andperforms delay correction on the basis of the updated optimum soundspeed to produce B-mode image data, B-mode image data is processed inthe DSC 24 and the image processor 26, and a B-mode image by thetransmission and reception in the N-th frame is displayed on the displayunit 30 as a still image according to the freeze instruction.

Alternatively, as the still image according to the freeze instruction,the B-mode image obtained by the normal transmission and reception inthe N-th frame and the B-mode image obtained by the transmission andreception for sound speed setting in the (N+1)th frame may be displayedin parallel. Further, selection means (selection instruction inputter)may be provided using the trackball 102 or the like, and only a selectedone out of the two B-mode images displayed in parallel may be displayed.

Any one of the display of only the B-mode image in the N-th frame, thedisplay of the B-mode image in the N-th frame and the B-mode image inthe (N+1)th frame, and the display of only the B-mode image in the(N+1)th frame may be selected by the mode or the like.

According to this embodiment, the operator can observe the B-mode imagewhen freeze is instructed by the FREEZE button 116, thereby it ispossible to perform diagnosis or the like. Further, the B-mode imagewhen freeze is instructed can be compared with the B-mode imageimmediately after the freeze, thereby it is possible to performobservation, diagnosis, or image selection.

In the invention, reception data in the first to N-th frames as well asreception data in the N-th frame or in the N-th and (N+1)th frames maybe stored in the reception data memory 36, reception data in the firstto N-th frames may be processed on the basis of the updated optimumsound speed to produce B-mode images, and the B-mode images may bedisplayed on the display unit 30 in parallel. Further, selection means(selection instruction inputter) may be provided in the operating device46, one or more images from the B-mode images displayed in parallel maybe selected, and only the selected image or images may be displayed.

Otherwise, reception data in the (N-n)th (where n is an integer lessthan N) to N-th frames may be stored, and the same processing may beperformed thereon. Furthermore, n may be selected by the operator.

In the invention, the B-mode images based on both of the optimum soundspeed before update used in the frames before the (N+1)th frame and theoptimum sound speed updated by the transmission and reception for soundspeed setting in the (N+1)th frame may be displayed.

In this embodiment, reception data obtained by the transmission andreception in all the frames immediately after the optimum sound speed islast updated, from the first one to the N-th one, is stored in thereception data memory 36.

In the ultrasound diagnostic apparatus 10, similarly to the above, asshown in FIG. 4, in a state where the normal transmission and receptionshown in FIG. 3A is repeatedly performed at a predetermined frame rate,and a motion image in the live mode is displayed, if freeze isinstructed in the N-th frame by the FREEZE button 116, as describedabove, the transmission and reception for sound speed setting isperformed in the subsequent (N+1)th frame to update the optimum soundspeed. In addition, the optimum sound speed before update, that is, theoptimum sound speed which is updated in the zero-th frame and is useduntil the N-th frame is stored in the signal processor 20.

After the optimum sound speed is updated, the signal processor 20 readsreception data in the first to N-th frames from the reception datamemory 36, and produces a B-mode image signal subjected to delaycorrection on the basis of the updated optimum sound speed and a B-modeimage signal subjected to delay correction on the basis of the optimumsound speed before update for each frame, and similarly to the above,the B-mode image signals are processed by the DSC 24 and the imageprocessor 26.

Subsequently, the B-mode images of the first to N-th frames based on theupdated optimum sound speed and the B-mode images of the first to N-thframes based on the optimum sound speed before update, both processed bythe image processor 26, are displayed on the display unit 30 inparallel.

Alternatively, selection means (selection instruction inputter) may beprovided in the operating device 46, and out of the B-mode imagesdisplayed in parallel, either the B-mode images based on the updatedoptimum sound speed or the B-mode images based on the optimum soundspeed before update as selected may solely be displayed. Further, one ormore B-mode images out of the B-mode images displayed in parallel may beselected, and only the selected B-mode image or images may be displayed.

In addition to these B-mode images, B-mode image a produced by thetransmission and reception for sound speed setting in the (N+1)th framemay be displayed.

According to this embodiment, for performing diagnosis or the like, theoperator can compare and observe the B-mode images which are observeduntil freeze is instructed and the B-mode images based on the optimumsound speed immediately after freeze is instructed. It is preferablethat the B-mode images as observed until freeze is instructed and theB-mode images based on the optimum sound speed immediately after freezeis instructed are compared by the operator and preferred image or imagesare displayed.

Also in this embodiment, reception data in the (N-n)th (where n is aninteger less than N) to N-th frames, instead of the first to N-thframes, may be stored, and the same processing as described above may beperformed. Furthermore, n may be selected by the operator.

In this embodiment, the B-mode image based on the optimum sound speedbefore update may be stored, for example, in the image memory 32 or thelike, and the image may be read therefrom and displayed.

Further, in the invention, one or more out of three display methods,namely, the display of the B-mode image in the (N+1)th frame based onthe updated optimum sound speed, the display of the B-mode image in theN-th frame (and the B-mode image in the (N+1)th frame) based on theupdated optimum sound speed, and the display of the B-mode image basedon the updated optimum sound speed and the B-mode image based on theoptimum sound speed before update, may be selected by mode selection orthe like.

As another embodiment, the FREEZE button 116 may be configured such thatit can be long pressed, and a still image may be displayed in accordancewith this operation of the FREEZE button 116.

In the ultrasound diagnostic apparatus 10, as conceptually shown in FIG.5, in a state where the normal transmission and reception shown in FIG.3A is performed at a predetermined frame rate, and a motion image in thelive mode is displayed, if freeze is instructed by the FREEZE button 116(FREEZE button ON), subsequently, the piezoelectric element array 14performs the transmission and reception for sound speed setting shown inFIG. 3B at a predetermined frame rate as conceptually shown in FIG. 4.

The frame rate of the transmission and reception for sound speed settingat this time may be different from the frame rate of the normaltransmission and reception.

While the FREEZE button 116 is ON, the transmission and reception forsound speed setting is repeatedly performed, and reception data issequentially stored in the reception data memory 36.

In the sound speed setter 40, the optimum sound speed is setcorrespondingly to all frames, in which the transmission and receptionfor sound speed setting is performed, in the similar way as describedabove and the set optimum sound speeds are supplied to the signalprocessor 20. The signal processor 20 reads reception data from thereception data memory 36, and performs delay correction based on thecorresponding optimum sound speed to produce a B-mode image signal. TheB-mode image signal is processed by the DSC 24 and the image processor26, and a motion image of the B-mode image by the transmission andreception for sound speed setting is displayed on the display unit 30 ata predetermined frame rate.

From this state, as shown in FIG. 5, if the FREEZE button 116 isreleased (FREEZE button OFF), the B-mode image in the frame (N-th frame)immediately before the release of the FREEZE button is displayed on thedisplay unit 30 as a still image according to the freeze instruction.Alternatively, still images of the B-mode images for n frames (where nis an integer less than N) before the N-th frame may be displayed on thedisplay unit 30.

That is, according to this embodiment, it is possible to display theB-mode image based on the sound speed at time point when freeze isinstructed.

In addition, in the ultrasound diagnostic apparatus 10 of theillustrated example, in a state where the normal transmission andreception shown in FIG. 3A is repeatedly performed in accordance with apredetermined frame rate, and the B-mode image in the live mode isdisplayed, also when the instruction on an observation target range isgiven by operation of the operating device 46, the transmission andreception for sound speed setting is performed in response to thisinstruction, and the optimum sound speed is updated.

Specifically, in the ultrasound diagnostic apparatus 10, it is assumedthat the normal transmission and reception shown in FIG. 3A is performedat a predetermined frame rate as described above, and the DEPTH button108 is operated during the B-mode image is displayed. In response tothis operation, that is, the instruction to change the observation depth(depth of visual field), the controller 42 gives an instruction to thetransmission circuit 16 and the reception circuit 18 so that thepiezoelectric element array 14 performs the transmission and receptionfor sound speed setting in the transmission and reception immediatelyafter the instruction to change the observation depth, and the soundspeed setter 40 sets the optimum sound speed and updates the optimumsound speed in a similar way as described above.

As an example, the DEPTH button 108 is a so-called neutral-off lockerswitch (seesaw switch), and performs operation (gives an instruction) toincrease and decrease the observation depth.

In the illustrated example, an end portion on a deep side of theultrasound image is moved in the depth direction to increase or decreasethe observation depth. However, in the invention, alternatively, an endportion on a shallow side of the ultrasound image may be moved in thedepth direction to increase or decrease the observation depth, or theincrease or decrease by movement of the end portion on the shallow sideand movement of the end portion on the deep side may be selected.

In the invention, change means (change instruction inputter) for theobservation depth is not limited thereto, and means for changing onlythe observation depth without changing the extent of the observationregion (the extent of the observation field) in the depth direction maybe provided. Alternatively, both means for increasing or decreasing theobservation depth and means for changing only the observation depthwithout changing the extent of the observation region may be provided.

In the ultrasound diagnostic apparatus 10, as conceptually shown in FIG.6A, when the normal transmission and reception shown in FIG. 3A isperformed at a predetermined frame rate, if an instruction to decreasethe observation depth is given in the N-th frame by the DEPTH button108, the transmission and reception for sound speed setting is performedin the next (N+1)th frame in response to this instruction.

FIG. 6B conceptually shows ultrasound images which are produced bytransmission and reception of an ultrasonic wave in individual frames.

When the instruction to decrease the observation depth is given by theDEPTH button 108, as transmission and reception for sound speed setting,the transmission and reception shown in FIG. 3B which forms five focusesfor setting for one scan line may be performed. However, when thedecrease of the observation depth is performed (an instruction to makethe end portion on the deep side shallower is given), an ultrasonic echois not received from a reduced deep region, and an ultrasound image isnot produced. Accordingly, it is purposeless to obtain the optimum soundspeed in this region, and transmission and reception which forms a focusfor setting in this region is not required.

For this reason, when the observation depth is decreased, as shown inthe (N+1)th frame of FIG. 6A, it is preferable that transmission andreception which forms a focus for setting at the deepest position oneach scan line in the transmission and reception for sound speed settingis not performed. That is, in this example, the transmission andreception for sound speed setting is performed four times for each scanline in accordance with the decrease of the observation depth.

After the transmission and reception for sound speed setting isperformed in the (N+1)th frame, as described above, reception datathereof is stored in the reception data memory 36, the signal processor20 reads reception data from the reception data memory 36, and theoptimum sound speed is set by the sound speed setter 40.

The sound speed setter 40 supplies the newly set optimum sound speed tothe signal processor 20, and the signal processor 20 updates the optimumsound speed. That is, in the ultrasound diagnostic apparatus 10, as apreferred embodiment, immediately after the instruction to decrease theobservation depth is performed by the DEPTH button 108, the transmissionand reception for sound speed setting is performed, and the optimumsound speed is updated.

After the optimum sound speed is updated, the signal processor 20 readsreception data by the transmission and reception for sound speed settingin the (N+1)th frame from the reception data memory 36 again, performsdelay correction on the basis of the updated optimum sound speed, andthereafter, as described above, a B-mode image signal is produced. Whenproducing the B-mode image signal, thinning or the like of receptiondata may be performed as necessary.

Similarly to the above, the B-mode image signal in the (N+1)th frameproduced by the signal processor 20 is processed by the DSC 24 and theimage processor 26, and is displayed on the display unit 30.

In the transmission and reception for sound speed setting in the (N+1)thframe, the B-mode image may not be produced, but only the setting of theoptimum sound speed may be performed. In this regard, the same appliesto different transmission and reception for sound speed setting.

After the transmission and reception for sound speed setting in the(N+1)th frame ends, the controller 42 gives an instruction to thetransmission circuit 16 and the reception circuit 18 so that thepiezoelectric element array 14 performs the normal transmission andreception for producing a B-mode image with a decreased observationdepth in the (N+2)th frame and afterward.

Here, the transmission and reception after the observation depth isdecreased may be the normal transmission and reception shown in FIG. 3A.However, as described above, when the decrease of the observation depthis performed, an ultrasound image is not produced for a reduced deepregion, and the transmission and reception which forms a transmissionfocus in this region is purposeless.

For this reason, when the Observation depth is decreased, it ispreferable that in the normal transmission and reception, thetransmission and reception which forms a focus for setting at thedeepest position on each scan line is not performed, as shown in the(N+2)th frame and afterward in FIG. 6A. That is, in this example, in thenormal transmission and reception, two transmissions and receptions areperformed for each scan line in accordance with the decrease of theobservation depth.

Similarly to the above, a reception signal by the normal transmissionand reception in the (N+2)th frame is processed into reception data andas such stored in the reception data memory 36. The signal processor 20reads reception data, performs delay correction on the basis of theupdated optimum sound speed to produce a B-mode image signal, anddisplays a B-mode image on the display unit 30. As conceptually shown inFIG. 6B, the B-mode image becomes an image having a decreasedobservation depth with no luminance in a deeper portion.

In the (N+3)th frame and afterward, the same normal transmission andreception and the production and display of the B-mode image arerepeatedly performed. In the case where the observation depth isdecreased, the frame rate is shortened in accordance with the decreasedobservation depth.

When the update of the optimum sound speed in the (N+1)th frame is toolate, the B-mode image may be produced on the basis of the optimum soundspeed used before the (N+1)th frame. In this regard, the same applies tothe update of the optimum sound speed in response to an instruction on adifferent observation target range (and an instruction to change imagequality and an instruction to change an image mode described later).

In the ultrasound diagnostic apparatus 10, also in the case where theincrease of the observation depth is instructed by the DEPTH button 108in a state where the observation depth is decreased as shown in FIGS. 6Aand 6B, similarly, the transmission and reception for sound speedsetting is performed and the optimum sound speed is updated.

That is, as conceptually shown in FIGS. 7A and 7B, in a state where theultrasound image having a decreased observation depth is produced anddisplayed by the normal transmission and reception according to adecreased observation depth, if an instruction to increase theobservation depth (in this example, an instruction to restore theobservation depth) is given in the N-th frame by the DEPTH button 108,in response to this instruction, the transmission and reception forsound speed setting is performed in the next (N+1)th frame.

Since the optimum sound speed is updated ahead in a depth region underobservation, the transmission and reception for sound speed setting whenincreasing the observation depth is a transmission and reception whichforms a focus for setting only in the extended depth region, as shown inFIG. 7A. That is, in this example, four transmissions and receptions intotal including two transmissions and receptions which form a focus forsetting and two transmissions and receptions which form a transmissionfocus for B mode forming are performed for one scan line.

However, when increasing the observation depth, the transmission andreception for sound speed setting of FIG. 3B for the formation offocuses for setting corresponding to the entire surface of theultrasound image may be performed. Further, when the transmission andreception for sound speed setting is performed, the optimum sound speedmay be updated over the entire surface in the same way as describedabove.

After the transmission and reception for sound speed setting isperformed in the (N+1)th frame, similarly to the above, reception datais stored in the reception data memory 36, the signal processor 20 readsreception data from the reception data memory 36, and the optimum soundspeed is set by the sound speed setter 40.

The sound speed setter 40 supplies the newly set optimum sound speed tothe signal processor 20, and the signal processor 20 updates the optimumsound speed. That is, in the ultrasound diagnostic apparatus 10, thetransmission and reception for sound speed setting is performedimmediately after the increase or decrease of the observation depth isperformed by the DEPTH button, and the optimum sound speed is updated.

After the optimum sound speed is updated, the signal processor 20 readsreception data by the transmission and reception for sound speed settingin the (N+1)th frame from the reception data memory 36 again, andperforms delay correction on the basis of the updated optimum soundspeed to produce a B-mode image signal. When producing the B-mode imagesignal, thinning or the like of reception data may be performed asnecessary.

The B-mode image signal in the (N+1)th frame produced by the signalprocessor 20 is processed by the DSC 24 and the image processor 26, andis displayed on the display unit 30.

After the transmission and reception for sound speed setting in the(N+1)th frame ends, the controller 42 gives an instruction to thetransmission circuit 16 and the reception circuit 18 so that thepiezoelectric element array 14 performs the normal transmission andreception shown in FIG. 3A for producing a B-mode image having anincreased observation depth.

In response to this instruction, as shown in FIG. 7A, in the (N+2)thframe and afterward, the normal transmission and reception shown in FIG.3A is repeatedly performed at a predetermined frame rate, and delaycorrection is performed on reception data obtained by the transmissionand reception on the basis of the updated optimum sound speed to producea B-mode image signal, and as shown in FIG. 7B, a B-mode image having anextended depth region is displayed at a predetermined frame rate.

If the observation depth is increased or decreased as described above,the reception time of the ultrasonic echo changes with the change of theobservation depth, and the frame rate also changes, accordingly.

In response to this, as described above, the frequency of the update ofthe optimum sound speed which is performed regularly, for example, oncefor every predetermined number of frames may be changed.

In the ultrasound diagnostic apparatus 10 of the illustrated example,also in the case where ROI setting is instructed as the instruction onan observation target range, the update of the optimum sound speed isperformed.

As an example, in the ultrasound diagnostic apparatus 10, in a statewhere a frame representing an ROI (a so-called ROI box) is notdisplayed, if the ZOOM button 82 is pressed, the ROI box is displayed inthe ultrasound image. Subsequently, the position of the ROI box isadjusted by the trackball 102, and the SET button 106 is pressed,whereby the position of the ROI box is determined. Thereafter, the sizeof the ROI box can be adjusted by operation of the trackball 102, andthe SET button 106 is pressed to determine the ROI.

It is possible to return to operation at a previous stage by pressingthe DELETE button 100 during operation.

In the ultrasound diagnostic apparatus 10, as shown on the left side ofFIGS. 8A and 8B, in a state where the normal transmission and receptionshown in FIG. 3A is performed and the B-mode image is displayed, asdescribed above, the display of the frame representing the ROI and theadjustment of the position and size of the ROI are performed, and then,the ROI is determined by the SET button 106.

In FIGS. 8A, 8B, and FIGS. 9A to 9C described later, reference characterR denotes the frame representing the ROI.

In response to this instruction to determine an ROI (that is, aninstruction to set an ROI), the controller 42 gives an instruction tothe transmission circuit 16 and the reception circuit 18 so that thepiezoelectric element array 14 performs the transmission and receptionfor sound speed setting in a frame immediately after the determinationinstruction. That is, in the ultrasound diagnostic apparatus 10, as apreferred embodiment, the transmission and reception for sound speedsetting is performed immediately after the ROI is set by thedetermination instruction, and the optimum sound speed is updated:

Here, in this transmission and reception, the transmission and receptionfor sound speed setting of FIG. 3B for the formation of focuses forsetting over the entire ultrasound image may be performed. However,preferably, as shown in FIG. 8B, transmission and reception in which afocus for setting is formed only in the ROI box, and a transmissionfocus corresponding to the normal transmission and reception is formedin the region other than the ROI is performed. Thereby, it is possibleto shorten the time required for the transmission and reception forsound speed setting in response to the instruction to set an ROI, whileenhancing the image quality in the ROI.

Similarly to the above, reception data obtained by such transmission andreception is sequentially stored in the reception data memory 36. Ifreception data is stored in the reception data memory 36, first, thesignal processor 20 reads reception data inside the ROI, and updates theoptimum sound speed in the ROI in the same way as described above.

After the optimum sound speed in the ROI is updated, next, the signalprocessor 20 reads reception data from the reception data memory 36, andperforms delay correction to produce a B-mode image signal. At thistime, regarding reception data inside the ROI, delay correction isperformed on the basis of the updated optimum sound speed, and regardingreception data in the region other than the ROI, delay correction isperformed on the basis of the optimum sound speed used before the ROIdetermination. Thereafter, the B-mode image is displayed on the displayunit 30 in a similar way to that described above.

In subsequent frames, the normal transmission and reception shown inFIG. 3A is performed at a predetermined frame rate, and reception datais processed to produce a B-mode image signal. Here, reception datainside the ROI is processed on the basis of the updated optimum soundspeed, and reception data in the region other than the ROI is processedon the basis of the optimum sound speed used before the determination ofthe ROI. The B-mode image is displayed at a predetermined frame rate.

In the ultrasound diagnostic apparatus 10, for example, movement of theset ROI and the extension and reduction of the set ROI can be performedby operation instructions through the DELETE button 100, the trackball102, and the SET button 106.

For example, as conceptually shown on an upper side of FIG. 9A, it isassumed that movement of the ROI is instructed, the ROI is moved, andthe ROI is determined by the SET button 106. In response to thisdetermination of the ROI, as shown on a lower side of FIG. 9A, thetransmission and reception as above, in which a focus for setting isformed in the ROI and a transmission focus corresponding to the normaltransmission and reception is formed in the region other than the ROI,is performed in the frame immediately after the determination accordingto the moved and determined ROI. Thereby, the optimum sound speed in theROI is updated, and a B-mode image signal is produced and displayed.

Subsequently, the normal transmission and reception shown in FIG. 3A isperformed at a predetermined frame rate, reception data is processed toproduce a B-mode image signal, and the B-mode image is displayed. Here,reception data inside the ROI is processed on the basis of the updatedoptimum sound speed, and reception data in the region other than the ROIis processed on the basis of the optimum sound speed used before thedetermination of the ROI.

As conceptually shown on an upper side of FIG. 9B, it is assumed thatthe extension of the ROI (the extension of the ROI box) is instructed,and the ROI is extended and determined. In response to this extensionand determination of the ROI, as shown on a lower side of FIG. 6B, thetransmission and reception, in which a focus for setting and atransmission focus corresponding to the normal transmission andreception are formed, is performed in the frame immediately after thedetermination according to the extended and determined ROI in a mannersimilar to the above, the optimum sound speed in the ROI is updated, anda B-mode image is produced and displayed.

Subsequently, similarly to the above, the normal transmission andreception shown in FIG. 3A is performed at a predetermined frame rate,reception data is processed to produce a B-mode image signal, and theB-mode image is displayed. Reception data inside the ROI is processed onthe basis of the updated optimum sound speed, and reception data in theregion other than the ROI is processed on the basis of the optimum soundspeed used before the determination of the ROI.

When the reduction of the ROI is performed, the update of the optimumsound speed may be performed similarly, or since the update of theoptimum sound speed in the ROI has been performed at the time of ROIsetting, the update of the optimum sound speed in the ROI may not beperformed.

In the above example, when the determination of the ROI is instructed bydetermination means (determination instruction inputter), thetransmission and reception for sound speed setting is performed, and theupdate of the optimum sound speed in the ROI is performed.

Here, even in a state where the determination is not instructed by theSET button 106, when there is no movement of the frame representing theROI or no change in size thereof in a state where the setting, movement,extension, reduction or the like of the ROI is instructed, it isconsidered that the operator has an interest in the region asrepresented by the frame. That is, when the frame representing the ROIstops, it is considered that the operator has an interest in the regionas represented by the frame.

Accordingly, in the invention, in a state where the setting, movement,extension, reduction or the like of the ROI is instructed, and beforethe determination of the ROI, when the ROI box stops for a predeterminedtime (for example, a predetermined time set appropriately between 0.5 to5 seconds, in particular, about 1 second) or more, this may be regardedas the instruction to determine the ROI, and the update of the optimumsound speed in the box (or the entire ultrasound image) may beperformed.

Alternatively, when the updated state of the optimum sound speedaccording to either the update of the optimum sound speed by thedetermination of the ROI or the update of the optimum sound speedaccording to the stopping of the frame representing the ROI is reached,the update of the optimum sound speed may be performed.

Further, two or more of the update of the optimum sound speed by thedetermination of the ROI, the update of the optimum sound speedaccording to the stopping of the ROI box, and the update of the optimumsound speed according to either the determination or the stopping of theROI may be selected.

As above, according to the invention, in the ultrasound diagnosticapparatus, when the instruction on an observation target range, such asan instruction to change in observation depth or set an ROI, is given,the transmission and reception for sound speed setting is performed inresponse to this instruction to update a sound speed, and thereafter,delay correction is performed on the basis of the updated sound speed toproduce a B-mode image.

Therefore, according to the invention, it is possible to stably displaya high-quality ultrasound image with no distortion or the like on thebasis of an accurate sound speed, correspondingly to an observationtarget range in which an ultrasound image is desired to be observed indetail.

In the ultrasound diagnostic apparatus 10, as shown on an upper side ofFIG. 9C, it is possible to enlarge (and reduce) an ultrasound imageinside the ROI using the ZOOM button 82 of the operating device 46.

In this case, the inside of the ROI is just enlarged and displayed, andas shown on a lower side of FIG. 9C, no instruction is given on anobservation target range. Accordingly, when the enlargement of theultrasound image inside the ROI is performed, in particular, the updateof the optimum sound speed may not be performed.

However, when the ultrasound image inside the ROI is enlarged, it isconsidered that this is to observe the ROI in more detail.

For this reason, when the enlargement of the ultrasound image inside theROI is performed, transmission and reception for sound speed setting inwhich the density of the focuses for setting in the ROI is higher thanthe density of the focuses for setting in the transmission and receptionfor setting shown in FIG. 3B may be performed in response to thisinstruction so as to update the sound speed in the ROI.

For example, as shown in FIG. 9C, if a displayed image becomesapproximately an image inside the ROI by the enlargement of theultrasound image, the transmission and reception for sound speed settingis performed so that five focuses for setting are formed for one scanline in the ROI. Accordingly, in regard to one scan line, it is possibleto perform the update of the optimum sound speed in the ROI more closelywith the same number of times of transmission as the transmission andreception for sound speed setting shown in FIG. 3B.

As described above, in the ultrasound diagnostic apparatus 10, theupdate of the optimum sound speed is performed at a regular timing ofonce for every predetermined number of frames.

At this time, in a state where the ROI is set as shown in FIGS. 8A and8B or 9A to 9C, a regular update of the optimum sound speed may beperformed only in the ROI or may be performed over the entire surface ofthe ultrasound image. However, if the update of the optimum sound speedonly in the ROI is continued over a long time (in multiple frames), asense of discomfort may arise between ultrasound images inside andoutside the ROI. For this reason, even when the regular update of theoptimum sound speed is performed only in the ROI, it is preferable toperform the update of the optimum sound speed over the entire surface ofthe ultrasound image at a frequency lower than the frequency of theupdate in the ROI.

In the above example, although change in observation depth and ROIsetting are illustrated as the instruction on an observation targetrange, the invention is not limited thereto.

For example, as the instruction on an observation target range,extension and reduction of an observation region (observation field) inthe azimuth direction, extension and reduction of an observation region(observation field) in both the azimuth direction and the depthdirection, enlargement and reduction (zoom-in and zoom-out) of anultrasound image, or the like may be used. Accordingly, instructionmeans (instruction inputter) for instructing the observation targetrange may be provided in the operating device 46, and in response to theinstruction on an observation target range given by the instructionmeans, the transmission and reception for sound speed setting may beperformed, the optimum sound speed may be updated, and thereafter, anultrasound image may be produced.

In the ultrasound diagnostic apparatus 10 of the illustrated example,even in a state where the normal transmission and reception shown inFIG. 3A is repeatedly performed at a predetermined frame rate, and theB-mode image in the live mode is displayed, if change in image isinstructed by operation through the operating device 46, in response tothis instruction, the transmission and reception for sound speed settingis performed, and the update of the optimum sound speed is performed.

In the ultrasound diagnostic apparatus 10, it is assumed that in a statewhere the normal transmission and reception shown in FIG. 3A isperformed at a predetermined frame rate, and a motion image in the livemode is displayed, the GAIN dial 114 is operated to give an instructionto change a gain. In response to this instruction, the controller 42gives an instruction to the transmission circuit 16 and the receptioncircuit 18 so that the piezoelectric element array 14 performs thetransmission and reception for sound speed setting shown in FIG. 3B inthe transmission and reception immediately after the instruction tochange a gain is given, and similarly to the above, the sound speedsetter 40 sets the optimum sound speed and performs the update of theoptimum sound speed.

That is, as conceptually shown in FIG. 10A, in the ultrasound diagnosticapparatus 10, in the above-mentioned state where the normal transmissionand reception shown in FIG. 3A is performed at a predetermined framerate, and the B-mode image is displayed, if change in gain is performedin the N-th frame by the GAIN dial 114, the transmission and receptionfor sound speed setting shown in FIG. 3B is performed in the next(N+1)th frame in response to this instruction.

FIG. 10B conceptually shows ultrasound images which are produced bytransmission and reception of an ultrasonic wave in individual frames.

After the transmission and reception for sound speed setting isperformed in the (N+1)th frame immediately after the GAIN dial 114 isoperated, similarly to the above, reception data is stored in thereception data memory 36, the signal processor 20 reads reception datafrom the reception data memory 36, and the optimum sound speed is set bythe sound speed setter 40.

The sound speed setter 40 supplies the newly set optimum sound speed tothe signal processor 20, and the signal processor 20 updates the optimumsound speed. That is, in the ultrasound diagnostic apparatus 10, as apreferred embodiment, the transmission and reception for sound speedsetting is performed immediately after gain change is instructed, andthe optimum sound speed is updated.

After the optimum sound speed is updated, the signal processor 20 readsreception data by the transmission and reception for sound speed settingfrom the reception data memory 36 again, and performs delay correctionon the basis of the updated optimum sound speed to produce a B-modeimage signal. When producing the B-mode image signal, thinning or thelike of reception data may be performed as necessary.

The B-mode image signal produced by the signal processor 20 is processedin the DSC 24 and the image processor 26, and is displayed on thedisplay unit 30.

In the subsequent (N+2)th frame and afterward, as shown in FIGS. 10A and10B, the normal transmission and reception shown in FIG. 3A isperformed, and reception data is processed on the basis of the updatedoptimum sound speed to produce a B-mode image signal.

In the ultrasound diagnostic apparatus 10 of the illustrated example,also when the STC key 68 is operated, in response thereto, thetransmission and reception for sound speed setting is performed, and theupdate of the optimum sound speed is performed.

As described above, the STC key 68 is operating means (operating unit)which performs gain adjustment for each depth region of the ultrasoundimage, individually. In the illustrated example, the STC key 68 canadjust the gain in each of six depth regions, individually.

As conceptually shown in FIG. 11A, in the ultrasound diagnosticapparatus 10, similarly to the above, in the above-mentioned state wherethe normal transmission and reception shown in FIG. 3A is performed at apredetermined frame rate, and the B-mode image is displayed, if the STCkey 68 is operated in the N-th frame to change the gain at any depth,the transmission and reception for sound speed setting shown in FIG. 3Bis performed in the next (N+1)th frame.

Similarly to FIG. 10B, FIG. 11B conceptually shows ultrasound imageswhich are produced by transmission and reception of an ultrasonic wavein individual frames.

In this example, it is assumed that the second STC key 68 from thebottom (for the second deepest depth region) is operated.

The transmission and reception for sound speed setting in the (N+1)thframe corresponding to operation of the STC key 68 may be thetransmission and reception for sound speed setting shown in FIG. 3B inwhich focuses for setting are formed over the entire surface of anultrasound image, and the update of the optimum sound speed over theentire surface is performed.

However, a depth region in which the gain is not adjusted is a regionfor which the operator determines that image quality of the ultrasoundimage has no problem. Accordingly, in this depth region, it is notnecessary to dare to perform the update of the optimum sound speed.

For this reason, in the transmission and reception for sound speedsetting corresponding to operation of the STC key 68, as shown in FIG.11A, the transmission and reception for sound speed setting is performedso that a focus for setting is only formed correspondingly to the depthregion in which the gain is adjusted, and the same transmission focusesas those in the normal transmission and reception are formed in theother depth regions. Thereby, it is possible to shorten the timerequired for the transmission and reception for sound speed setting inresponse to the instruction to change a gain, while enhancing the imagequality of the image in the depth region in which the gain is changed.

After the transmission and reception for sound speed setting isperformed in the transmission and reception in the (N+1)th frameimmediately after the STC key 68 is operated, similarly to the above,reception data is stored in the reception data memory 36. The signalprocessor 20 reads reception data obtained by the transmission to andreception from the transmission focus for sound speed update from thereception data memory 36. Using the read reception data, the sound speedsetter 40 sets the optimum sound speed in the region in which thetransmission focus for sound speed update is set, that is, the depthregion for which change in gain is instructed.

The sound speed setter 40 supplies the newly set optimum sound speed tothe signal processor 20, and the signal processor 20 updates the optimumsound speed of the depth region in which change in gain is instructed.That is, also in this example, as a preferred embodiment, thetransmission and reception for sound speed setting is performedimmediately after gain change is instructed by the STC key 68, and theoptimum sound speed is updated.

After the optimum sound speed is updated, the signal processor 20 readsreception data, which is obtained by the transmission to and receptionfrom the transmission focuses for B mode production in the transmissionand reception for sound speed setting, from the reception data memory36, and performs delay correction on the basis of the updated optimumsound speed to produce a B-mode image signal.

The B-mode image signal produced by the signal processor 20 is processedin the DSC 24 and the image processor 26, and is displayed on thedisplay unit 30.

In the (N+2)th frame and afterward, as shown in FIGS. 11A and 11B, thenormal transmission and reception shown in FIG. 3A is performed, andreception data is processed on the basis of the updated optimum soundspeed to produce a B-mode image signal.

As described above, according to the invention, in the ultrasounddiagnostic apparatus, in response to the instruction to change imagequality, the transmission and reception for sound speed setting isperformed immediately after the change in image quality is instructed toupdate the sound speed, and an ultrasound image is produced on the basisof the updated sound speed.

Therefore, according to the invention, it is possible to produce anultrasound image at an accurate sound speed by updating a sound speed atan appropriate timing when the operator wants to improve image quality,and thus to produce a high-quality ultrasound image with nodeterioration of image quality due to distortion or the like.

In clinical practice, during diagnosis, if a plurality of switchesshould be operated by the operator, this may cause erroneous operation.Accordingly, an increase in the number of switches to be operated duringdiagnosis causes a problem. In contrast, in the invention, the soundspeed is updated with the instruction to change image quality as atrigger. Therefore, according to the invention, it is possible to updatethe sound speed at an appropriate timing without providing a switchwhich instructs to update a sound speed, so as to produce an ultrasoundimage of high-quality.

In the above example, the update of the optimum sound speed is performedwhen either of the GAIN dial 114 and the STC key 68 is operated.However, the invention is not limited thereto.

That is, in the invention, the optimum sound speed may be updated onlywhen operation is performed corresponding to either the GAIN dial 114 orthe STC key 68. Alternatively, selection means (selection instructioninputter) may be provided in the operating device 46, and any of theupdate of the optimum sound speed corresponding to operation of eitherof the GAIN dial 114 and the STC key 68, the update of the optimum soundspeed corresponding to operation of only the GAIN dial 114, and theupdate of the optimum sound speed corresponding to operation of only theSTC key 68 may be selected.

Further, in the ultrasound diagnostic apparatus 10 of the illustratedexample, the transmission and reception for sound speed setting isperformed at the timing when operation of the GAIN dial 114 or the STCkey 68 starts. However, the invention is not limited thereto.

For example, the transmission and reception for sound speed setting maybe performed at the timing when operation of the GAIN dial 114 or theSTC key 68 is determined. Alternatively, the inventive apparatus may beconfigured such that the transmission and reception for sound speedsetting is performed when operation of the GAIN dial 114 or the STC key68 starts, and the update of the optimum sound speed is performed usingreception data obtained by the preceding transmission and reception forsound speed setting at the timing when operation of the GAIN dial 114 orthe STC key 68 is determined. In addition, the inventive apparatus maybe configured such that when the amount of operation of the GAIN dial114 or the STC key 68 exceeds a predetermined threshold value, thetransmission and reception for sound speed setting is performed toupdate the optimum sound speed. These configurations may be selected bythe mode or the like.

In the above example, as the instruction to change image quality of anultrasound image that is accompanied with the update of the optimumsound speed, gain adjustment is illustrated.

However, in the ultrasound diagnostic apparatus 10 of the invention, theoperating device 46 may additionally have at least one of dynamic range(contrast) adjustment means (adjustment instruction inputter), gradationcurve processing (map) adjustment means (gradation curve processinginstruction inputter), sharpness adjustment means (adjustmentinstruction inputter), and speckle noise removal processing instructionmeans (speckle noise removal processing instruction inputter), and whenchange (adjustment) in image quality is instructed corresponding to atleast one of dynamic range, sharpness, gradation curve processing andspeckle noise removal processing of an ultrasound image, the update ofthe optimum sound speed may be performed. Out of these instructions tochange image quality, any may be selected as an instruction accompaniedwith the update of the optimum sound speed.

In the ultrasound diagnostic apparatus 10 of the invention, such changesin image quality may be performed using known image processing or thelike. Further, such changes in image quality may be performed on theentire ultrasound image or carried out through means having a functionof performing adjustment for each of predetermined depth regions, suchas the STC key 68.

Further, in the ultrasound diagnostic apparatus 10, in theabove-mentioned state where the normal transmission and reception shownin FIG. 3A is repeatedly performed in accordance with a predeterminedframe rate, and B-mode image in the live mode is displayed, also whenthe instruction to change the image mode is given by operation of theoperating device 46, the transmission and reception for sound speedsetting is performed, and the update of the optimum sound speed isperformed.

In the ultrasound diagnostic apparatus 10, it is assumed that in a statewhere the normal transmission and reception of FIG. 3A in a fundamentalwave mode (hereinafter, also referred to as “FI mode”) is performed at apredetermined frame rate, and a motion image in the live mode isdisplayed, the HARMONICS button 80 is pressed to instruct to switch theimage mode to the THI mode. In response to this instruction, thecontroller 42 gives an instruction to the transmission circuit 16 andthe reception circuit 18 so that the piezoelectric element array 14performs the transmission and reception for sound speed setting of FIG.3B in the THI mode in the transmission and reception immediately afterthe change in mode is instructed, and similarly to the above, the soundspeed setter 40 sets the optimum sound speed and updates the optimumsound speed.

That is, in the ultrasound diagnostic apparatus 10, as conceptuallyshown in FIG. 12A, in a state where the normal transmission andreception of FIG. 3A in the FI mode (at a frequency of f₁ in bothtransmission and reception) is performed at a predetermined frame rate,and the B-mode image is displayed, if the HARMONICS button 80 is pressedin the N-th frame and change to the THI mode is performed, in responseto this instruction, the transmission and reception for sound speedsetting shown in FIG. 3B is performed in the next (N+1)th frame in theTHI mode in which an ultrasonic wave (fundamental wave) at a frequencyof f₁ is transmitted and an ultrasonic echo as a harmonic of thefundamental wave (e.g., a second harmonic (at a frequency of 2f₁)) isreceived.

FIG. 12B conceptually shows ultrasound images which are produced bytransmission and reception of an ultrasonic wave in individual frames.

After the transmission and reception for sound speed setting isperformed in the transmission and reception in the (N+1)th frameimmediately after the change to the THI mode is instructed, similarly tothe above, reception data is stored in the reception data memory 36, thesignal processor 20 reads reception data from the reception data memory36, and the optimum sound speed is set by the sound speed setter 40.

The sound speed setter 40 supplies the newly set optimum sound speed tothe signal processor 20, and the signal processor 20 updates the optimumsound speed. That is, in the ultrasound diagnostic apparatus 10, as apreferred embodiment, the transmission and reception for sound speedsetting is performed immediately after the change to the THI mode isinstructed, and the optimum sound speed is updated.

After the optimum sound speed is updated, the signal processor 20 readsreception data by the transmission and reception for sound speed settingfrom the reception data memory 36 again, and performs delay correctionon the basis of the updated optimum sound speed to produce a B-modeimage signal. When producing the B-mode image signal, thinning or thelike of reception data may be performed as necessary.

The B-mode image signal produced by the signal processor 20 is processedin the DSC 24 and the image processor 26, and is displayed on thedisplay unit 30.

In the (N+2)th frame and afterward, as shown in FIGS. 12A and 12B, thenormal transmission and reception shown in FIG. 3A is performed in theTHI mode in which the ultrasonic wave at a frequency of f₁ istransmitted and the ultrasonic echo as a second harmonic of thefundamental wave that has a frequency of 2f₁ is received, and receptiondata is processed on the basis of the updated optimum sound speed toproduce the B-mode image signal in the THI mode.

Further, in the ultrasound diagnostic apparatus 10, also when modechange from the FI mode to the CH mode is performed, similarly to theabove, the update of the optimum sound speed is performed.

That is, as conceptually shown in FIG. 13A, in the ultrasound diagnosticapparatus 10, it is assumed that in a state where the normaltransmission and reception of FIG. 3A in the FI mode (at a frequency off₁ in both transmission and reception) is performed at a predeterminedframe rate, and the B-mode image is displayed, the COMPOUND button 78 ispressed in the N-th frame to instruct to change the image mode to the CHmode. In response to this instruction, the transmission and receptionfor sound speed setting shown in FIG. 3B is performed in the next(N+1)th frame in the CH mode in which an ultrasonic wave at a frequencyof f₁ is transmitted, and an ultrasonic echo as a fundamental wave at afrequency of f₁ and an ultrasonic echo as a harmonic of the fundamentalwave (e.g., a second harmonic (at a frequency of 2f₁)) are received.

FIG. 13B conceptually shows ultrasound images which are produced bytransmission and reception of an ultrasonic wave in individual frames.

After the transmission and reception for sound speed setting isperformed in the transmission and reception in the (N+1)th frameimmediately after the change to the CH mode is instructed, similarly tothe above, reception data is stored in the reception data memory 36, thesignal processor 20 reads reception data from the reception data memory36, and the optimum sound speed is set by the sound speed setter 40.

The sound speed setter 40 supplies the newly set optimum sound speed tothe signal processor 20, and the signal processor 20 updates the optimumsound speed.

After the optimum sound speed is updated, the signal processor 20 readsreception data by the transmission and reception for sound speed settingfrom the reception data memory 36 again, and performs delay correctionon the basis of the updated optimum sound speed to produce a B-modeimage signal. The B-mode image signal produced by the signal processor20 is processed in the DSC 24 and the image processor 26, and isdisplayed on the display unit 30.

In the (N+2)th frame and afterward, as shown in FIGS. 13A and 13B, thenormal transmission and reception shown in FIG. 3A is performed in theCH mode in which the ultrasonic wave at a frequency of f₁ istransmitted, and the ultrasonic echo at a frequency of f₁ and theultrasonic echo as the second harmonic at a frequency of 2f₁ of thefundamental wave are received, and reception data is processed on thebasis of the updated optimum sound speed to produce the B-mode imagesignal in the CH mode.

In the example shown in FIGS. 13A and 13B, in the CH mode, transmissionof an ultrasonic wave is performed only once. However, the invention isnot limited thereto, and in the CH mode, two (or more) transmissions ofan ultrasonic wave may be performed, and the images obtained may besynthesized.

That is, as conceptually shown in FIGS. 14A and 14B, in a state wherethe normal transmission and reception of FIG. 3A in the FI mode isperformed at a predetermined frame rate, and the B-mode image isdisplayed, if the COMPOUND button 78 is pressed to perform the change tothe CH mode, in the CH mode, the transmission and reception, in which anultrasonic wave at a frequency of f₁ is transmitted and ultrasonicechoes as a fundamental wave at a frequency of f₁ and as a harmonic at afrequency of 2f₁ of the fundamental wave are received, and thetransmission and reception, in which an ultrasonic wave at a frequencyof f₂ (f₁<f₂) is transmitted and an ultrasonic echo at a frequency of f₂is received, may be performed.

As described above, according to the invention, in the ultrasounddiagnostic apparatus, in response to the instruction to change the imagemode, the transmission and reception for sound speed setting isperformed immediately after the change of the image mode is instructedto update the sound speed, and an ultrasound image is produced on thebasis of the updated sound speed.

Therefore, according to the invention, it is possible to produce anultrasound image at an accurate sound speed by updating the sound speedat an appropriate timing immediately after the image mode is changed,and thus to produce a high-quality ultrasound image with nodeterioration of image quality due to distortion or the like immediatelyafter the image mode is changed.

In the above example, as switching of the image mode, switching from theFI mode to the THI mode and switching from the FI mode to the CH modeare illustrated. In the ultrasound diagnostic apparatus 10, thetransmission and reception for sound speed setting is performed so as toupdate the optimum sound speed also when switching from the THI mode tothe FI mode, switching from the CH mode to the FI mode, switching fromthe THI mode to the CH mode, and switching from the CH mode to the THImode are each instructed.

In a state where the B-mode image is displayed, when the B button 94 orthe like is pressed, the transmission and reception for sound speedsetting may similarly be performed so as to update the optimum soundspeed.

In the above example, the optimum sound speed is updated correspondinglyto all instructions to switch the image mode including switching fromthe FI mode to the THI mode, switching from the FI mode to the CH mode,switching from the THI mode to the FI mode, switching from the CH modeto the FI mode, switching from the THI mode to the CH mode, andswitching from the CH mode to the THI mode.

However, the invention is not limited thereto. That is, in theinvention, the update of the optimum sound speed may be performedcorrespondingly to only one or more out of the instructions to switchthe image mode. The switching of the image mode accompanied with theupdate of the optimum sound speed may be selected by operation of theoperating device 46 or the like.

Further, also when switching to so-called frequency compounding orspatial compounding is instructed, similarly, the update of the optimumsound speed may be performed.

Moreover, in the above example, when the display of the ultrasound imagein the B mode is being performed, the update of the optimum sound speedis performed if the switching of the image mode is instructed.

However, in the ultrasound diagnostic apparatus 10 of the invention, theoptimum sound speed may similarly be updated also in the case where, forinstance, a similar switching of the image mode is performed when anultrasound image is being displayed in the M mode. A display modeaccompanied with the update of the optimum sound speed may be selectedaccording to the switching of the image mode.

In the ultrasound diagnostic apparatus 10 of the illustrated example,when any instruction out of the instruction of freeze, the instructionon the observation target range, the instruction to change imagequality, and the instruction to change the image mode is given, thetransmission and reception for sound speed setting is performed, and theoptimum sound speed is updated. However, the invention is not limitedthereto.

For example, the update of the optimum sound speed may be performedcorrespondingly to only one instruction or only two or threeinstructions out of the instruction of freeze, the instruction on theobservation target range, the instruction to change image quality, andthe instruction to change the image mode. Furthermore, one or moreinstructions accompanied with the update of the optimum sound speed maybe selected by mode selection or the like.

Further, in the above example, the transmission and reception for soundspeed setting for updating the optimum sound speed is performed in oneframe. However, the invention is not limited thereto. The formation ofthe focus for setting may be performed in plural frames, and the updateof the optimum sound speed over the entire screen may be performed inthe plural frames.

As an example, when performing the update (setting) of the optimum soundspeed in response to each of the instructions described above, in thefirst frame, as shown in FIG. 15A, a focus for setting is formed only onthe first scan line from the left of the drawing, and a transmissionfocus corresponding to the normal transmission and reception is formedon other scan lines, whereby the optimum sound speed is updatedcorrespondingly to the focus for setting.

In the next, second frame, as shown in FIG. 15B, a focus for setting isformed only on the second scan line from the left of the drawing, and atransmission focus corresponding to the normal transmission andreception is formed on other scan lines, whereby the optimum sound speedis updated correspondingly to the focus for setting.

In the next, third frame, as shown in FIG. 15C, a focus for setting isformed only on the third scan line from the left of the drawing, and atransmission focus corresponding to the normal transmission andreception is formed on other scan lines, whereby the optimum sound speedis updated correspondingly to the focus for setting.

In the next, fourth frame, as shown in FIG. 15D, a focus for setting isformed only on the fourth scan line from the left of the drawing, and atransmission focus corresponding to the normal transmission andreception is formed on other scan lines, whereby the optimum sound speedis updated correspondingly to the focus for setting. In this way, theoptimum sound speed may be updated over the entire screen (the entiresurface of an ultrasound image) in four frames in total.

Alternatively, a focus for setting may be formed for each depth, insteadof each scan line, so as to update the optimum sound speed at one depthin one frame. For example, in the example shown in FIG. 3B, focuses forsetting may be sequentially formed in ascending order of the depth, witha focus for setting at one depth being formed in one frame, and theoptimum sound speed may be updated over the entire screen in fiveframes.

Furthermore, one or plural focuses for setting may be formed in oneframe, and the update of the optimum sound speed may be performed foreach focus for setting. For example, in the example shown in FIG. 3B,one focus for setting may be formed in one frame, and the optimum soundspeed may be updated over the entire screen in 20 frames.

So far, the ultrasound diagnostic apparatus, the method of producing anultrasound image, and the recording medium of the invention have beendescribed in detail based on the examples, but the invention is notlimited thereto, and various improvements and modifications may be ofcourse made without departing from the gist of the invention.

The invention can be suitably used for ultrasound diagnosis which isused for various kinds of diagnoses in clinical practice or the like.

What is claimed is:
 1. An ultrasound diagnostic apparatus comprising: apiezoelectric element array which has piezoelectric elements arrangedtherein, each piezoelectric element configured to transmit an ultrasonicwave, to receive an ultrasonic echo reflected by a subject, and tooutput a reception signal according to a received ultrasonic wave; acontroller which controls ultrasonic transmission and reception by thepiezoelectric element array; a storage which stores the reception signaloutput from the piezoelectric element array; a sound speed setter whichsets a sound speed in the subject using the reception signal stored inthe storage; an image producer which processes the reception signaloutput from the piezoelectric element array or the reception signal readfrom the storage, based on the sound speed set by the sound speed setterto produce an ultrasound image; a display; and an operating device whichhas a freeze instruction inputter configured to instruct to display astill image on the display, an observation target range instructioninputter configured to specify an observation target range of anultrasound image displayed on the display, an image quality changeinstruction inputter configured to instruct to change image quality ofthe ultrasound image, and a mode change instruction inputter configuredto instruct to change an image mode of the ultrasound image, wherein thecontroller causes the piezoelectric element array to perform ultrasonictransmission and reception for sound speed setting so as to allow thesound speed setter to set the sound speed in response to at least oneinstruction out of an instruction to display a still image from thefreeze instruction inputter, an instruction on the observation targetrange from the observation target range instruction inputter, aninstruction to change image quality from the image quality changeinstruction inputter, and an instruction to change an image mode fromthe mode change instruction inputter, the sound speed setter sets thesound speed in the subject using a reception signal obtained by theultrasonic transmission and reception for sound speed setting to updatethe sound speed, the image producer processes the reception signaloutput from the piezoelectric element array based on an updated soundspeed to produce an ultrasound image, and the display displays theultrasound image produced by processing based on the updated soundspeed.
 2. The ultrasound diagnostic apparatus according to claim 1,wherein the controller causes the piezoelectric element array to performthe ultrasonic transmission and reception for sound speed setting inresponse to any instruction out of the instruction to display a stillimage from the freeze instruction inputter, the instruction on theobservation target range from the observation target range instructioninputter, the instruction to change image quality from the image qualitychange instruction inputter, and the instruction to change an image modefrom the mode change instruction inputter.
 3. The ultrasound diagnosticapparatus according to claim 1, wherein the controller causes thepiezoelectric element array to perform the ultrasonic transmission andreception for sound speed setting immediately after the instruction isgiven.
 4. The ultrasound diagnostic apparatus according to claim 1,wherein the sound speed setter divides the subject into a plurality ofregions and sets the sound speed for each region, and the image producerprocesses the reception signal based on the sound speed set for eachregion to produce an ultrasound image.
 5. The ultrasound diagnosticapparatus according to claim 1, wherein the image producer processes thereception signal obtained by the ultrasonic transmission and receptionfor sound speed setting based on the updated sound speed to produce anultrasound image in response to the instruction to display a still imagefrom the freeze instruction inputter.
 6. The ultrasound diagnosticapparatus according to claim 1, wherein the image producer processes areception signal output from the piezoelectric element array duringultrasonic transmission and reception before the ultrasonic transmissionand reception for sound speed setting based on the updated sound speedto produce an ultrasound image in response to the instruction to displaya still image from the freeze instruction inputter.
 7. The ultrasounddiagnostic apparatus according to claim 6, wherein the image producerprocesses a reception signal output from the piezoelectric element arrayat least during ultrasonic transmission and reception immediately beforethe ultrasonic transmission and reception for sound speed setting basedon the updated sound speed to produce an ultrasound image.
 8. Theultrasound diagnostic apparatus according to claim 1, wherein inresponse to the instruction to display a still image from the freezeinstruction inputter, the image producer processes a reception signaloutput from the piezoelectric element array during ultrasonictransmission and reception before the ultrasonic transmission andreception for sound speed setting based on the updated sound speed toproduce an ultrasound image after update of the sound speed, andprocesses the reception signal based on a sound speed set before theupdate of the sound speed to produce an ultrasound image before theupdate of the sound speed, and the display displays the ultrasound imageafter the update of the sound speed and the ultrasound image before theupdate of the sound speed.
 9. The ultrasound diagnostic apparatusaccording to claim 8, wherein the operating device has a selectioninstruction inputter configured to select either the ultrasound imageafter the update of the sound speed or the ultrasound image before theupdate of the sound speed, and when selection is made by the selectioninstruction inputter, the display only displays the ultrasound image asselected.
 10. The ultrasound diagnostic apparatus according to claim 1,wherein the observation target range instruction inputter includeseither or both of an observation depth change instruction inputterconfigured to instruct change in observation depth and a region ofinterest setting instruction inputter configured to instruct setting ofa region of interest.
 11. The ultrasound diagnostic apparatus accordingto claim 10, wherein the region of interest setting instruction inputterhas a region of interest determination instruction inputter configuredto instruct determination of a region of interest, and when a region ofinterest is determined through the region of interest determinationinstruction inputter, the controller, considering that the instructionon the observation target range is given, causes the piezoelectricelement array to perform the ultrasonic transmission and reception forsound speed setting.
 12. The ultrasound diagnostic apparatus accordingto claim 10, wherein the region of interest setting instruction inputterhas a region of interest movement instruction inputter configured toinstruct movement of a region of interest and a region of interest sizechange instruction inputter configured to instruct change in size of aregion of interest, and when no operation is performed through theregion of interest movement instruction inputter or the region ofinterest size change instruction inputter for a predetermined time in astate where the setting of a region of interest is instructed, thecontroller, considering that the instruction on the observation targetrange is given, causes the piezoelectric element array to perform theultrasonic transmission and reception for sound speed setting.
 13. Theultrasound diagnostic apparatus according to claim 10, wherein theobservation depth change instruction inputter has an extension andreduction instruction inputter configured to increase and decrease theobservation depth, and the sound speed setter updates the sound speedonly for a region extended or reduced through the extension andreduction instruction inputter configured to increase and decrease theobservation depth.
 14. The ultrasound diagnostic apparatus according toclaim 1, wherein, when the instruction on the observation target rangeis given by the observation target range instruction inputter, thecontroller causes the piezoelectric element array to perform theultrasonic transmission and reception for sound speed setting to form atransmission focus for sound speed setting corresponding to theobservation target range thus specified, and the sound speed setter setsand updates the sound speed in the subject according to the observationtarget range thus specified.
 15. The ultrasound diagnostic apparatusaccording to claim 1, wherein the image quality change instructioninputter instructs to change image quality of the ultrasound image for apredetermined region, when change in image quality for the predeterminedregion is instructed by the image quality change instruction inputter,the controller causes the piezoelectric element array to perform, withrespect to the predetermined region, the ultrasonic transmission andreception for sound speed setting so as to allow the sound speed setterto set the sound speed, and the sound speed setter sets a sound speed inthe predetermined region using the reception signal obtained by theultrasonic transmission and reception for sound speed setting to updatethe sound speed.
 16. The ultrasound diagnostic apparatus according toclaim 1, wherein change in image quality of the ultrasound imageaccording to the instruction to change image quality from the imagequality change instruction inputter is performed by either or both ofchange of an amplification factor for amplifying the reception signaland image processing in the image producer.
 17. The ultrasounddiagnostic apparatus according to claim 15, wherein the image qualitychange instruction inputter has a function of instructing the change inimage quality for each depth region set in advance, and when a depthregion for which image quality is to be changed is specified by aninstruction from the image quality change instruction inputter, thesound speed setter only updates the sound speed in the specified depthregion.
 18. The ultrasound diagnostic apparatus according to claim 1,wherein the image quality change instruction inputter has at least oneof a gain adjustment instruction inputter configured to adjust gain ofan ultrasound image, a dynamic range adjustment instruction inputterconfigured to adjust dynamic range of an ultrasound image, a gradationcurve processing instruction inputter configured to process gradationcurve of an ultrasound image, a sharpness adjustment instructioninputter configured to adjust sharpness of an ultrasound image, and aspeckle noise removal processing instruction inputter configured toinstruct removal of speckle noise from an ultrasound image.
 19. Theultrasound diagnostic apparatus according to claim 1, wherein the imagemode is any of a fundamental wave mode, a tissue harmonic mode, and acompound harmonic mode.
 20. The ultrasound diagnostic apparatusaccording to claim 1, wherein the image producer processes the receptionsignal obtained by the ultrasonic transmission and reception for soundspeed setting based on the updated sound speed to produce an ultrasoundimage.
 21. A method of producing an ultrasound image, the methodcomprising the steps of: performing ultrasonic transmission andreception for sound speed setting so as to set a sound speed in asubject in response to at least one instruction out of an instruction tofreeze to display a still image, an instruction on an observation targetrange of an ultrasound image, an instruction to change image quality ofan ultrasound image, and an instruction to change an image mode of anultrasound image; setting the sound speed in the subject using areception signal obtained by the ultrasonic transmission and receptionfor sound speed setting; processing an ultrasonic reception signal basedon the sound speed to produce an ultrasound image; and displaying theultrasound image.
 22. The method of producing an ultrasound imageaccording to claim 21, wherein, if any instruction out of theinstruction to freeze to display a still image, the instruction on anobservation target range of an ultrasound image, the instruction tochange image quality of an ultrasound image, and the instruction tochange an image mode of an ultrasound image is given, the ultrasonictransmission and reception for sound speed setting is performed and thesound speed in the subject is set.
 23. The method of producing anultrasound image according to claim 21, wherein the ultrasonictransmission and reception for sound speed setting is performedimmediately after the instruction is given, and the sound speed in thesubject is set.
 24. The method of producing an ultrasound imageaccording to claim 21, wherein the sound speed is set for each regionobtained by dividing the subject into a plurality of regions, and theultrasound image is produced based on the sound speed set for eachregion.
 25. A recording medium having recorded thereon a program formaking an ultrasound diagnostic apparatus display an ultrasound image,the program causing a computer to execute: a transmission and receptionstep of performing ultrasonic transmission and reception for sound speedsetting so as to set a sound speed in a subject in response to at leastone instruction out of an instruction to freeze to display a stillimage, an instruction on an observation target range of an ultrasoundimage, an instruction to change image quality of an ultrasound image,and an instruction to change an image mode of an ultrasound image; asound speed setting step of setting the sound speed in the subject usinga reception signal obtained in the transmission and reception step; animage production step of processing an ultrasonic reception signal basedon the sound speed set in the sound speed setting step to produce anultrasound image; and a display step of displaying the ultrasound imageproduced in the image production step on a display.
 26. The recordingmedium according to claim 25, wherein, in the transmission and receptionstep of the program, the ultrasonic transmission and reception for soundspeed setting is performed in response to any instruction out of theinstruction to freeze to display a still image, the instruction on anobservation target range of an ultrasound image, the instruction tochange image quality of an ultrasound image, and the instruction tochange an image mode of an ultrasound image.
 27. The recording mediumaccording to claim 25, wherein, in the transmission and reception stepof the program, the ultrasonic transmission and reception for soundspeed setting is performed immediately after the instruction is given.28. The recording medium according to claim 25, wherein, in the soundspeed setting step of the program, the sound speed is set for eachregion obtained by dividing the subject into a plurality of regions, andin the image production step, the ultrasound image is produced based onthe sound speed set for each region.